Was listening to a colleague of mine on the radio in a lengthy interview. He's a former ref and is currently a referee observers for UEFA matches (former refs who go to games to give back reports on how well the refs do their job). One point he made about how VAR is poorly implemented in England and frankly done wrongly is the misuse of "clear and obvious error". The VAR protocols that the VAR refs adhere by and the training they receive states that the reveiws should be done very quickly. If a VAR review takes a long time and/or you have many VAR stoppages in one match then the refs are doing something wrong. They are supposed to be quickly determined because it's not clear and obvious if multiple angles and slow-motion can't change the on-field verdict.
He also said that another big problems with the refs is that they are afraid to make decisions. They would rather not do anything and let VAR correct them. They should be much more confident in making on-field calls. Game is supposed to be refereed for the most part the same as it was before VAR, just in the cases where there are obvious big mistakes VAR steps in and only then.
He called Szymon Marciniak the current best ref in the world because he makes his own calls, takes no shit from players and very rarely does VAR intervene in his matches.