In the first game, if a planet gets culture swapped by anyone, it flips to neutral completely. Now culture only affects buffs, and flipping can only be done with specific abilities in conjuction with culture. It makes the culture game less vital and offensive culture less viable.

In games as Advent against Impossible AI, I can only win by ignoring the offensive culture game, building just a single Temple of Communion if I see their culture coming, while focusing entirely on fleet size and Titan timing. I shouldn't have to do that, culture should be equally as viable just like in Sins1.

Perhaps the consequences of losing culture should be more drastic and/or investing in offensive culture should yield more rewards.
Or perhaps the having less fleet size than the enemy should be less punishing, through the buffing of defenses and defensive strategies, so that we'd have more time and resources to invest into the culture game to break the stalemate, without worrying about losing the fleet size war/Titan timing war and thus the game.