Only Jesus, Ederson, and Dias have hit the ground running under Pep. Kolorov was really good at centre half under Pep too.
Even the established players struggled compared to their best form in Pep’s first season.
Like you say, Grealish hasn’t been brilliant, but he’s been quite good. Poor or more fairly, ineffective, at times; very good at others.
Pep is still working out his best attributes by playing him in different roles. Jack is still learning how to play under Pep. As always, next season is the best time to judge. However, that shouldn’t mean people shouldn’t call out poor and ineffective performances and say things like “he’s going to have to be better and more effective than that if he wants to make it at City” because that’s true, but are only observations about individual performances.