Managers are just not that important when you drill down hard on player performance or even strategy/wins. But at the end of the day the team is winning more games than it did last year and would, IMO, be easily on pace to win 90 games if things had broken right. Mostly injuries but ultimately Klentak had too much faith in the starting pitchers, and Franco and Herrera too.
And I'm not sure the theory that our individual players aren't living up to their potential holds up to scrutiny:
Realmuto, as it turns out, might be having a career year, because everything about his defensive game has improved here. He's putting up the second-best OPS of his career and may yet have his best offensive season ever. He's one of the best players in baseball.
Harper's well on his way to having a normal or even very good year, especially if you value RISP (which people seem to). On top of that his OPS is currently the fourth-highest of his career (in eight season) and may end up third. The things that are wrong with him were already wrong with him last year.
Segura is actually out-performing his career OPS and has also raised his OBP.
Hoskins' is obviously not getting it done lately and yet his OPS is still second-best on the team and better than last year.
Hernandez is disappointing but I think he's just injured/aging/declining.
Kingery's been great.
And this is a team that thinks with one brain, between the GM, the manager, the analytics department, and the coaching staff. Changing the manager won't change that unless the owner or MacPhail decide to really shake things up.