Culture is just a part of the game.  You can build your own culture centers to beat back or at least to hold enemy culture at bay if you need to.  If the opposition has several planets that are right next to your home terran and they're culture bombing you from it then you're probably in very bad shape anyway.  The best way to prevent something like that might be to keep them from taking planets near your terran in the first place and perhaps to take their planets down instead.

That would set Advent back at a disadvantage, and would remove an important aspect of economy in the game. Bad idea.

I tend to agree that culture is part of the game, and at any rate a cultural takeover is extremely rare and usually happens either when you're in such a bad position you're going to lose anyways or if you've got an outpost in the middle of enemy territorty.

In any case, there wouldn't be a huge difference if cultural takeover was removed from the game.  Your planet's loyalty would still be reduced to 0, causing all its income to disappear.  You'd still be able to build stuff there, I guess, but you'd still get no income from it.

You said turn of cultural takeovers, you said nothing about turning off culture altogether.  Interpreting you literally, your game setting would still cause loyalty to decrease to 0, but you just wouldn't lose control of the planet.