I have seen there are some posts mentioning people treat Grealish and other players differently. And it is true, but that always happens. Both transfer fee and wages make Grealish one of, if not, the most expensive player for City (he is the 3rd highest wage after all). But there are 3 important aspects besides that:
1. Grealish has been playing with City 22 months (not counting world cup and summer breaks). He has been excellent for 7 months (mid-October to mid-April of last year). That's like 33% of the time he's been excellent. The rest he has been just ok, sometimes even underwhelming. Compare that to Alvarez or Haaland (to say a new player). Both have been excellent most of the time. And let's not even bring people like KDB, Bernardo, Rodri or Dias who all have been exceptional for the last 3 seasons. If Dias is having a poor start of the season (which he is), you know that is the exception, and we all know he will come back to his normal level because he has shown what his level is for a looong time. But with Grealish, we don't know: were those 7 months his real level or an exception? Doubting him and criticizing him is more logical that any of those guys.
2.Highest ceiling. Let's say Rodri plays awful for the next month or that when KDB comes back from injury he is terrible for 2 months. They would keep being starters, Grealish would not, why? Because the highest level of KDB and Rodri might be the best level we have in our squad (and probably in the world), and everyone knows how much of a difference their highest level can produce for us, so you keep giving them minutes to recover their form. The benefit is way above of those 1-2 months of subpar level. Can we say the same for Grealish? No, his best level with us (those 7 months) and the level from Doku right now are not that different (I would still have that Grealish as a starter, but the difference is really small). Why would Pep risk 1-2 months of subpar level when he has a player that is doing great, and the other player at his highest level is not that much better than present Doku? Logically, Grealish has less minutes to show he is regaining form.