Thank you and thank you,
First of all, considering your thinking of AAA multiplayer games - for AAA game visuals are more important (market share matters more than the game). Bugs and glitches do not escape devs, they know about their existence but in the whole production, their priority will be lower (so low that it'll be decided to be fixed after release). Between releasing the game and fixing one small bug, what is more important? and there are hundreds in between.