Bosk, I agree with what you say, for the most part, but I'd say the case here is a bit different. Playing an instrument is also a very physical activity. Let's compare this to an athlete, for example: that person needs to work regularly, if not daily, but not to get better, just to mantain their current skill level/hability. If they want to get past that, that's where they have to push it. Playing an instrument is no different, it DOES take time and effort to mantain your current progress, because if you don't "practice" it, you lose it. Anyone who plays an instrument past the beginner stage knows this.
I'll use myself as another example, I've been a bass player for about 12 years now. While it's true that at first my practice routines looked very differently than now, as I'm not a professional musician or doing much gigs anymore and have a lot other things to do/worry about than sitting and playing, when I DO get to play, my self imposed task is to, at last, get to the "peak" I already got before, so that I don't lose it.
To take this even further, I was away in Mexico when the pandemic hit and got stuck there for more than 3 months, I'll finally be able to get home next week. I haven't touched a bass in more than 4 months, and when I get back, it's going to be very hard just to get to the point where I was before my travels.
About MP, I don't think anyone here is saying he doesn't sit and practice anymore, but rather that he doesn't raise the bar at all. Yes, he's VERY involved in the writing/recording process of whatever album he puts out, but when it comes to his drumming, it seems that he doesn't want to improve anymore, he just mantains the same level/skill set he's had since the Awake/FII era. And, as I said, that does take time and effort, but I'd say it's safe to assume he isn't improving his craft anymore. Whether that's good or bad, it depends really, but at least I would expect a professional musician in the prog rock/metal world, who's considered to be a virtuoso player and one of the best, to get serious about constantly improving, and that's possible (See: Mangini).