I think the biggest issue is that we're just not getting the basics right. Forget the football or system, but set pieces are the bread and butter of all teams through the entire football pyramid.
It's shocking how poor we are at defending them, and how poor we are attacking through them.
He's failed to get on top of that issue since he's arrived, and arguably the issues gotten worse since he's been here. You can't expect to win games, knowing we're going to start every game 1 goal down. This needs to be fixed before anything else.
By the same measure, we need to be more threatening when we have our own. That doesn't mean that I expect us to get a goal a game from them, but the amount of wasted set pieces we have drives me nuts. It's clear that we just don't spend anywhere near enough time on them in training.
The other thing I've been adamant about since he joined here, is that he needs to solidify the middle of pitch - at least while everyone's still learning the system. Chelsea's Conte are the blueprint to make this system work, and they had Kante and Matic in the middle. You need 2 players that can hold the pitch, so that your wide CBs can contest the spaces out wide so that your wingbacks can afford to be "lazy" defensively. Even Amad, at RWB gets pinned too far back back.
To make this system work, in possession you need this 3-2 set up, so that when you lose the ball the space you willingly give to teams is down the wide channels but it's your CBs who are defending down the channels, and your midfielders cut off space in the middle.
Forget Chelsea, Man City's treble winning side also ended up in this set up in attack.
-------Rodri--Stones
-----LCB---CCB---RCB
That team won the treble just 2 seasons ago, so it's not as if this set up can't work. Our problem is that aside from Ugarte, that second person in midfield isn't enough of a defensive presence. So he needs to find a way to either get Casemiro or Collyer in the team, or if he doesn't believe they're good enough he needs to do something clever like get one of the wingbacks to invert into midfield, and get one of the forwards to shuffle out wide.