I didn’t have any objections to your gnolls 
Plus, we both agree that 5e Insane Plague Gnolls are dumb. So bridges are being made!
Yep! I’m cool with gnolls worshipping Yeenoghu and this leading many of them to full on Evil with a capital E rather than savagery, and with Flinds as demonic gnolls that can show up in certain cases, but making the whole race fully supernaturally demonic ruins what I thought was a really cool concept.
This is why I keep harping on the “what do you mean by ‘evil’?” question. It sounds like your drow are congenitally non-empathetic; is that accurate? If the curse is that Llolth removed their ability to feel compassion, then that could be pretty interesting, with nifty ramifications. A society of remorseless sociopaths could still function, it’d be rational egoism writ large, a giant prisoner’s dilemma experiment. But in such a society, treachery would be dealt with, rationally, through the use of aversive measures unconstrained by any sense of mercy.
Much like in many human societies.
Or does the curse actually encourage treachery, say, by linking it to a pleasure response? Do drow betray one another because it makes their naughty bits tingle, per Llolth’s curse? That’s a different version of “always evil,” where a drow who acts honorably is like a vampire who forgoes human blood.
If the curse simply forces them to betray one another, though, I’m not sure that leaves much room for niftiness.
A Drow version of Bartertown?
This is a great point- as noted earlier, I like the idea that Lolth simply created Drow society and molds it to her will by guiding her priestesses (in my worlds it is generally the evil deities who are most involved on a day to day basis with their followers). But if I was to have her curse directly affecting individual drow to make them evil, I’d go about it with a very specific curse: impatience. Which Lollth herself wouldn’t really consider a curse, since that’s basically what got her kicked out of the elven pantheon, IIRC
CJ Cherryh wrote a sci-fi series about humans co-existing with, coincidentally enough, a race of humanoid, ebony-skinned aliens who, due to the way they evolved from pack hunters, do not have the concept of “friendship.” They’re literally incapable of liking someone the way humans do - the closest analogy they can come up with is liking a salad. This fundamental incompatibility led to repeated situations where the aliens acted in what, to humans, were shocking acts of betrayal, but to the aliens made perfect sense, based on their complicated society that evolved out of pack hierarchy disputes. The aliens weren’t evil, just… alien. But it still nearly led to a war of extinction with the humans until they learned how to get along.
That’s the kind of thing I love: societies that are internally complex, and deeply hostile to our eyes, but not out of any sort of moustache-twirl. There’s a novel, Eifelheim, that does something similar, with an insectoid alien race who doesn’t (IIRC) feel empathy, but does feel joy; also, they find the idea of music and dancing to be delightful gibberish and just can’t get enough of watching humans do it and trying (with complete incompetence) to do it themselves.
I run most of my campaigns in Pathfinder’s Golarion setting. In that setting, the drow exist because of a demonic curse, but it’s a curse that’s been laid on the entire elven species. Any elf can potentially become a drow by “giving into despair,” which the setting didn’t really rigorously define. I interpreted it as someone abandoning their moral principles and committing evil after losing hope of achieving their goals any other way. At one point, the PCs were put on trial by a secret elven society dedicated to suppressing outside knowledge of the existence of the drow, and were able to exonerate themselves by goading the societies leader until he got so mad he spontaneously transformed. Looking back, the implications of “His villainy is proven when his skin turned black” is definitely cringey, and I’d probably do it differently today. On the other hand, I did get to do the climax to Pleasantville in a D&D campaign.
Anyway, the thing about drow in that setting is, they still have giant subterranean cities full of drow. They don’t spell it out, but I came away with the impression that drow have normal elven children, who are raised to become drow by the time they’re adults.
I like this, too. I think when you are dealing with a more mundane creature, like an orc or a drow (as opposed to a demon), simply saying “they are always evil” is unsatisfying. Two more questions have to be answered: in what specific way are they evil? And, why?
If the “why” is “because Lollth/Gruumsh/whoever cursed them to be evil” that’s fine in a fantasy setting, but you still have to explain how exactly the curse manifests itself and how it changes their society.
And of course, there is Planescape, which asks these same questions about demons and archons alike, and where your bartender may well be a devil while the big bad is an angel.
By the way - this was before I got to the thread, but - why are people hating on non-Lawful-Good Paladins? 
why should Lawful Good deities be the only ones who get holy warriors to smite their enemies?
This happens all the time. Your car breaks down and the only two mechanics in town are shady. But you still need your car fixed so you do what you can to protect yourself. And the mechanic may vary “fuck people over” based on circumstances from “overcharge for labor” to “Lie about needed repairs” to “Hold off this time because this guy doesn’t seem fooled and will beat the shit out of me”. Even crooked mechanics can still get cars fixed and you aren’t going to be fucking people over 24/7 because that way lies self-destruction. A Drow performing a task is probably 50% looking for an edge, 30% watching over their shoulder and 20% on the task at hand. They still need buildings built and bathrooms remodeled and clothes sewn and the upper classes impose laws to keep society more or less on the rails, mostly as a tool and pretext to keep the lower classes under some control and the lights on.
Inefficient? Absolutely. But they can get away with it in part due to the spans of time involved. And it also answers the issues of why these Drow aren’t expansionist and the age old RPG question of “If you elves have a civilization a bajillion years old, why are you still using bows and arrows like humans?” In the case of the Drow, it’s at least partially because shit happens slowly and inefficiently and corruptly. If they were a human society trying to pull this shit off, they’d be screwed.
And, of course, it’s an RPG world and you can paper over things with “A Lloth did it” and “Because it makes a better game that way” and “If you just wasted two hours debating Drow society instead of rolling dice, people are going to go home.”
I was luke warm to the idea until I read the Rose of the Prophet Trilogy which features a Lawful Evil paladin who I thought was well realized. I can get behind other paladins. I’m not as keen on Chaotic paladins since that seems to go against the idea of a holy order but since I’ve never run a campaign where someone played a chaotic paladin, it’s a moot point.
We clearly play with very different groups 
Paladins in earlier editions were very narrow character concepts - they were holy questing knights in the vein of Arthurian legend and had all sorts of rules meant to enforce that image.
Nowadays paladins are just militant clerics of any religion. Since it’s a change from a traditional take, lots of people hate it by default.
That’s still a Paladin of Pelor [or Insert LG Deity Here].
But if Lollth has a holy order of spiked chain wielding knights who ride spiders into battle to smite her enemies, why can’t they be Paladins too?
They can! I don’t mind the change at all, even though I do have a soft spot for the LG grail knight archetype.
I’ve only played one paladin in the past 20 years or so. What I thought was a cool concept–a warforged paladin of vengeance intended as a bodyguard to a cleric of Moradin but who went rogue due to his programmatic understanding of ethics and justice, and who lacked a concept of self or first-person–ended up torpedoing a negotiation with a mob boss, and possibly ending a 10-year campaign :(.
Not giving paladins another chance anytime soon.
It’s just preference. I liked the old school paladin as an absolute paragon of good represented by the Lawful Good alignment. There’s nothing wrong with preferring the paladin as they are now.
I prefer the old LG paladins. For the reason you gave. I did have some problems with the idea that a paladin must be constantly entering knightly tournaments and such. I once played a paladin who turned down an opportunity to duel. At least one other player thought this was wrong. I had my character explain “I fight against the forces of evil and for the causes of (I forget what deity it was). These things are worth killing and dying for. A trophy is a meaningless piece of metal. It is NOT worth fighting for.”
I understand preferring the LG paladin - but that paladin still exists, if someone plays a Lawful Good paladin. All that the new rules have done is add a number of new paladin types that are now available.
Maybe they should have left the paladin alone and created an entirely new class for the evil variant.
I remember (but don’t have a copy of) an anti-paladin article in Dragon. IIRC the character got uglier and uglier until the mere sight of their face paralysed good creatures. They got bonuses for attacking weaker creatures.