Always gotta blame someone. Hard to quibble with Castro but I think the raw material was probably more of an issue than how they were coached (or positioned). Dillon seems a bit more puzzling. Like, one reason they hired him was his history with Harper and that seems to be working out well. And even Bohm was coming around before the COVID break. Hitting coach can't stop Cutch, Didi and JT from aging.
I'd be more impressed if they got a new bench coach. Thomson is both a Klentak/Kapler holdover and Girardi's longtime wingman; seems to me Joe, not being an especially great manager himself IMO, could use a fresh voice/differing perspective in the dugout. Of course anyone they hired, especially if Fuld and Dombrowski had some say, would be perceived as the next manager too. (I don't think Dusty can count on that ever happening for him either, though he'd certainly be qualified for that promotion, and while he's not exactly new-school, he'd still be a fresh voice with a history of working with young players).