There are quite a few old hands among Python core devs. Certainly the culture of that burnout is in place, if you look at the responses that proposals for new standard library additions get these days. There also seems to be a lot of trauma from the loud complaints about backward compatibility breaks.

I still hear people complain about how such and such removal between "minor versions" of Python 3 (you really should be thinking of them as major versions nowadays — "Python 3 is the brand", the saying goes now), where they were warned like two years in advance about individual functions, supposedly caused a huge problem for them. It's hard for me to reconcile with the rhetoric I've heard in internal discussions; they're so worried in general about possible theoretical compatibility breaks that it seems impossible to change anything.