What Arteta has done at Arsenal or Klopp and Guardiola have done at Liverpool/City is that they've implemented a idea that has then developed into something where their teams have a strong build up phase, which allows them to dominate the game. And without having the ability to control the first phase of the build up they can't control the game. And if you can control the first phase, you control the game and hence push the opponent back into a deeper block.
And the reason the first phase of the build up is important to control (especially nowadays) is because many teams have now adopted the method of defending from the front, in packs. And if your players are weak on the ball in the build up phase then it will be a struggle to progress play through the opponent's coordinated pressure, which will mean it will be difficult to effectively progress the play. And the build up begins with the free man in the first phase who will be the goalkeeper. The goalkeeper has to be strong in that regard and take the initiative when it comes to breaking a line or clipping a ball to either fullback whilst being pressured.
For United to become a proactive attacking team with the added ability to aggressively press high up the pitch, control has to be exerted in the build up phase. You can't control the game in possession without controlling the first phase against teams who press high. And for us to close the gap on Arsenal and City, we have to collectively upgrade upon those players who are weak on the ball when it comes progressing play (effectively) in the build up phase.
So like I've said before, we need a RB, GK and CM who provide a high level of technical security on the ball. And if we can get the right players in who take the initiative on the ball, instead of passing responsibility on to others. We will at the very least be taking steps towards creating a proactive attacking team, which will have the potential to dominate the ball in a compact high block.
The likes of Arsenal, City and even Brighton score more goals than us, create more goals than us and create more chances generally due to their teams being superior to us in the first phase of the build up. So it's not a surprise a player like Mitoma at Brighton is very productive due to him playing in a team that is setup to exert control which allows for more possessional control and more possesion.
The return of Casemiro and Eriksen will hopefully get us UCL football, then it depends on what we've got to spend.
This is a great summary.
Football styles change, and at the moment the high press is king. Even mid-level PL clubs are drilled to do it very well. So, as you've pointed out, top teams have focused on being able to play out from the back more than ever. We can't do it very well, so a huge chunk of PL teams are set up with the tools to hurt us.
For what it's worth, it's obvious that EtH knows this. It's why he signed Martinez and Anthony (gets a lot of stick for not being direct, but his role is to help us keep possession high up the pitch), and wanted FdJ. It's why he uses Eriksen deeper with Casemiro. Neither of them are ideal for helping to play out from the back and still get caught out more than he'd like, but they're better than anything else we have at the moment. When they're both not playing it really gets painful watching our first build up phase.
The problem is that I don't see us adequately fixing each of those problem positions you've highlighted this summer. Mainly because signing a ST is such a big issue to deal with first. This is why we'll probably have to persevere with DDG for the time being. My hope is that we at least get in a better RB or a young CM more suitable to play this way, preferably both, so at least we're not so reliant on Casemiro/Eriksen being available.
I don't think it's fair to blame EtH for a lot of the issues we've seen lately, like some on this site have started to do. The issues were always there, he had just done a really good job of finding work arounds up until now. Something had to give, and I just think the build up of games, lack of prep time between them, and mostly the loss of too many key personnel, has finally caught up with him. People even seem to forget that we lost Garnacho for the rest of the season, who is our only direct attacker and genuine goal threat after Rashford. It shouldn't be an 18 year old playing his first season in the senior squad, but it just is right now.
The squad is just so out of touch in some areas with what a title winning team needs to be at the moment, and that's down to the lack of future planning and recruitment from the board. I also don't think Ole understood this, and seemed to be focusing much more on being a counterattack team long term, as he saw this as the 'United Way'. Because of this we're now stuck with players like Maguire and AWB. Strong defenders, but pretty useless in the first build up phase or playing a high line. EtH would have never signed these guys.