In my opinion it single-handedly makes both defending & attacking worse. The defending part is obvious, constant mindless player switching as the ball is passed around trying to block a million passing lanes per second as no other player will do so on his own.
On the attacking front, your passing game is transformed from having to watch all opponent players and pick your passes carefully, to just avoiding the one player who is allowed to defend/intercept.
This is probably worse for the game than having to constantly player switch. A bad pass should not work, no matter if it's intercepted by a human or an AI player. It was a bad pass to begin with.
So, it's something that makes defending sweaty & monotonous and attacking much more trivial and less enjoyable. If everyone enjoys attacking football as much as they say they are, then shouldn't the skill gap be in attacking and in creating the space and wouldn't that be much more enjoyable? I think it's all a bit backwards... Yay, let's make a football game with a focus on player switching and let's make attacking and scoring goals trivial and joyless! Sounds fun.