So, as far as I can see we're pretty much here:
We can't really play 3 at the back (whether it's 343, 352 or 3412) as anything other than a defensive formation because we can't press, and the positions that demand the most quality (wing backs and central midfield) are the ones where we have least of it.
We can't really play 4222 because we can't press, and because the full backs don't provide the needed width so the two AMs have to do that instead. Which collapses the formation to a 424 when we have the ball, which is a) a shit formation to begin with and b) leaves our two CMs with way too much on their hands.
We can't really play 4231 because we can't press or stay compact, and our CM gets dominated defensively and can't provide functional link-up play, and playing as a lone striker doesn't suit Ronaldo.
We can't really play 442 diamond, because we can't press and our full backs and CMs don't provide enough attacking input.
We probably shouldn't really play 433, because we can't press, the full backs don't provide enough attacking input and we'd have to either drop or use suboptimally our key offensive player. Plus, it leaves Ronaldo a lone striker again.
In other words, until we get better CMs, we look like we're screwed. And why are we allowing Kieran Trippier to sign for Newcastle, for a transfer sum no bigger than we were prepared to pay this summer? No indications at all so far that the club is willing to support Rangnick in the transfer market.