After some playing around, I think Stellaris has some major issues, partly built on its quasi-basis in Europa Universalis.
First, there’s a huge lack of fixed defenses. Yes, they exist, but they’re nothing more than a speedbump to an actual warfleet. Where this becomes an issue, is that it turns every war into a massive war. In this game, ever war turns out like a Mahan-idealized naval war, entirely dependent on one gigantic battle. Even with a bunch of bonuses to building ships, it almost impossible to rebuild after a major loss. Once you take serious losses, the enemy (whether that’s the player or AI) can simply roll right over you.
Second, a third party may get called into a war where it has nothing to gain and no interest, and will hurl its entire fleet into the fight. (This was a problem in EU as well, because the AI would throw everything into every single warm which was basically a design to keep the player from picking around the edges of a a powerful empire - even though that was actually a pretty logical and common reaction in real life.)
Third, Hyperdrive… does not work well with the game set. I think it’s the most interesting one to use, but IMHO, it only works if that’s the only allowable FTL method. The upgrade to Jump/Psi Jump is fine; it’s just that the hyperspace lanes don’t interact well with opponents who ignore them from day 1. In addition, because of the way the game generates them, the lanes make no sense as laid out (since they are supoosed to have been developed deliberately) and often have weirdly impractical whorls or branches. In addition again, there’s no way for the player to ever remedy this by adding their own, presumably for a major cost in energy and some minerals.
Fourth, the galaxy generator ends up being way, way too random. You can be completely wrecked by a bad start in so many ways, and even having two guaranteed-decent, habitable planets nearby isn’t enough.
Fifth, if’n I had my druthers, they’d change the planet model such that anybody could reasonably inhabit any world with a biosphere, but each species, having its own preferred terrain, are only happy on tiles that match their climate. So, in effect, planets no longer have climates - tiles do. The nature of the planet would only affect this insofar as it controls how many tiles are allocated to different climates. My thought is that hydrosphere would be a major challenge to overcome, but climate a smaller penalty, on the grounds that it’s a lot easier to live in a cold or hot climate than one with virtually no water or an actual ocean, if you’re used to dry land with regular rainfall.
This could be used way to add new specialized technologies, like “Ocean Habitats” or “Artificial Hydrosphere” to make otherwise-uninhabitable places useful. It also makes it more of a strategic choice for the player, since they would have to decide where to ignore a region of space, use a pricey colony ship to claim a world where they can only use 2 tiles for the foreseeable future, or place an expensive and Influence-draining outpost to save it for later when the planet might be worthwhile.
And, oh yeah, 1.5 Banks is awesome.