The thing is, there are a LOT of different reasons a season can suck. New writers trying different things, cast leaving, budget cuts, and on and on and on. Two shows I enjoyed season 1 of and disliked (for very different reasons) the second (and last) seasons of.
Dark Angel (2000) was a dystopian police state of future America, after an EMP dropped out tech into ‘has-been’ status, with genetically engineered super-soldiers in hiding and a heroic underground reporter trying to make things just a little bit better, and getting the truth out there. The supporting cast was fun, if overblown, but didn’t detract from the story. Not perfect, but fun.
Season two dropped 80-90% of the first seasons storylines and much better developed villain (who is a villain but not utterly irrational) to replace it all with an ancient cult and monster (bio-engineered) of the week episodes. The supporting cast were introduced hurriedly and it felt like you were being ‘told’ to like them, rather than feel like they were likeable. And suddenly, the majority of the governmental distrust was shifted to the cult, which, well, just didn’t work. (see the dates for likely reasons).
Jericho (2006) - was a drama based on the scenario of the modern US hit by a wide ranging series of presumably terrorist related nuclear detonations in many (23) major cities and the fallout, both literal and figurative thereof in a small Kansas town. There’s small town drama, interfamily drama, survival drama with deep undercurrents of a huge conspiracy behind the events. Again, not a perfect show, in that it (IMHO) spread itself too thin between a huge cast and TOO much drama and internal conflict, but I enjoyed it.
Season two only came about because of a massive write in campaign, as it was cancelled after the first 22 episode season, and was giving a total of 7 episodes, during which they were a lot more focused on the underlying story (based on a deep state fracturing of the government for increased autocratic/plutocratic control) and the conflicts between the town and the newly established militaristic state.
The focus was a good idea, but it was an abrupt near 180 from the direction of season one, and just jarring. And 7 episodes was never going to be enough to get past that point especially with the major changes - sure if it had been amazingly successful it could have spawned another mini-season or other continuation but no one honestly expected it. Or they could have tried to wrap up the story in said 7 episodes instead of trying to fix everything and maybe get renewed or picked up by another network. It’s one of those shows where I almost wish they just hadn’t bothered, and left the story as it was at the end of season one instead of having the mutated post script that was season 2.
( and yes, I’m aware that there was a comic based continuation/completion of the storyline but at that point I no longer cared, it was all about finishing [poorly] the conspiracy story, which I only cared about in CONJUNCTION with the personal stories )