I just think he's slumping, not done. We're not talking about a Nick Castellanos or even a Rhys Hoskins here. He had a great year in the field last season too. In the end he had a very good year the year he struggled previously as well.
WAR-wise he was worth well more than his salary last year and he'll probably match it this year too (his salary, not the great WAR from last year). We've won two division titles with him, and 95/96 games. He needs to be better this year, but he's not really the problem. The Phillies' failure to get anything from a RHB at RF or 3B remains the problem. In the end Turner will be 4th on the team in WAR this year (heck, he's already 5th, behind JT, and that's also a credit to Marsh).
And catchers are tough to come by. It's unfortunate the Phillies got squeezed by JT after he misplayed their hand with Bichette but I don't believe this would be a better team with any other catcher they might have signed or acquired (be even worse if they'd paid Caratini less). It does seem a little odd they moved on from Tait so easily when Marchan doesn't look like anything, but that wouldn't matter for the next three seasons anyway. And O'Hoppe isn't good either.
At some point you have to flush the first month of this season. Phillies are probably playing as well as any team in baseball for the past month even if the pitching-first/weak offense formula isn't always fun. And if we're lucky Garcia is another one of those free agents who struggled in a new city with new coaching and is starting to figure it out. If he's not, well, we're back to where we've been every other season in RF.