I've been struggling with the defense myself. The AI is just so incredibly passive and incapable of reading the play coming at them. I finally got my AFC Richmond team promoted to the Premier League, and our first game against Man City was a 3-0 blowout because the AI is just so awful at reading the play. Similarly, I barely held on to a 2-1 win against Tottenham, again, because my CB's just constantly stand still behind the oncoming play, just waiting until the attackers are literally passing them to finally turn and try to catch up, which isn't happening when it's two players in the high 70's for speed against the likes of Kane, Son and Davies running in full speed.
I want to hold out hope, but seeing as EA hasn't even patched out the slider reset but, among others I'm sure I haven't noticed yet, I'm guessing it's just going to be continued frustration...