Not sure who says they leave a lot of space "behind", or maybe you aren't explaining properly what you mean. The main problem with the way the cpu is putting players on the field is that they essentially compress backwards whenever you attack, making the game an enormous attack vs defence.
@Matt10 did a lot of detailed videos and posts about this issue, go see them if you haven't.
In real life, at you never see a defender marking a forward only to let him turn around for free. In real life the midfield isn't also the joke of Pes 2018. And, for final, picking up Hazard and Messi (aka the 1% of players) to make a general point on how defenders behave doesn't make sense to me.
Well I was mainly playing top player, so it mitigated the effect, otherwise the more you play the more you realize the bullshit the cpu was at superstar and legend (a least pre patch). There is virtually no variety in the way CPU plays.
p.s. have some respect for your interlocutor as I do and format your posts, please. This should be a rule honestly, wall of texts like the ones you are doing hurt the eyes.