There's a reasonable explanation for why he hasn't used the new players as much as some would like (me included).
Very reasonable explanations, like you I'd like to see more of them too. Ignoring the obvious, we actually have quite a young squad to build on.
Reis was never going to start big games this season, he looks good, but needs to learn about the PL.
Khusanov was a signing brought forward due to a situation, he was thrust into the limelight right away as we literally had no one else, he was even voted player of the month, but once we had Akanji back he was going to struggle for games, and again he needs to learn the PL.
Nico has been up and down in the games he's played, some thought he was going to be Rodri, ridiculous, again young, doesn't know the PLand has a lot to learn, if it's true he had a go at Pep when subbed, then it was a bit silly, but I would think Pep actually liked that, rather than scapegoating him, and none of us know what goes on in training.
Omar was again brought in because we had a situation, he's done OK, should have played at Southampton, and I don't understand why he was taken off yesterday, as I thought he was one of few who looked like he was giving maximum effort.
As for the rest of the squad, McAtee isn't good enough in midfield in a Pep team, he doesn't work hard enough, Nunes has some good talent, but doesn't apply it well enough, he was doing OK at FB, and was improving, not sure he deserved to be left out, only Pep can explain the reasoning there. Doku does the same frustrating things every time he gets a game, he has a great skill set, but no brain to use it for the best. Savinho might be good, but he wasn't brought in to play a full season. I don't think he should start when Doku does, or vice versa, it just brings too much chaos. O'Reilly has been a great addition, and I'd like to see him further forward, and in the limited games Oscar has looked good.
None of us really know what is going on with Grealish or Foden, I never saw the hype with Grealish, and he seems to be the best player that never plays in some peoples eyes, yet when he gets on, does nothing. Phil is just burnt out for me, needs a lengthy break, and find a way to get back to some energy/enthusiasm for the game.
I don't think there as much to fix as some make out, injuries have taken a toll, some look knackered, some are done at this level, but I think Pep will sort it out, though we have to make the CL, as the players we need might not come for EL.