I think it's possible to believe he shouldn't play as much and also possible to believe there is no one better to play instead of him (including Pache who might be the best of them just in terms of trading offense for defense).
I think it's also possible to believe he was a bad signing to begin with and may never bounce back this year while also believing he could. It's not just what he did in the NLDS - it's that he was a productive offensive player for four of six months last year, and an elite one for two of them. Ideally he has four good months in him again this year. If he doesn't - if he's bad for three of the next four months - they need do do something. Right now, as the winningest team in baseball, they do not.
The only thing I don't believe is that he can change or improve. I think that ship sailed for him when he was still in his 20s. He is what he is and if the body and hand-eye is going, get out the checkbook for his replacement, Mr. Middleton (because it's not like there's an strong internal candidate for the next two seasons).
FWIW/SSS, Nick's OPS+ in the last 7 days is 122 (for obvious reasons) and in the last 14 days 94. That's not a trajectory I'd be looking to arrest, even if it's not necessarily meaningful/sustainable.