Can it get you to Marc Rebillet's [0] level in 5 years of a few hours per day practice? He makes it look so effortless and I can't even begin to imagine the flow state he's experiencing.
I feel like there's two different skill-sets at play--the ability to learn a piece, as printed, and play it back accurately, and then this, which is more improvisational skills. The two skill sets intertwine but mastery of one does not necessarily transfer.
To learn the latter quickly, I find it easiest to build a catalogue of music you like listening to, and then figure out how to transcribe it (by ear) on your piano. Maybe just the most overt melody lines at first, before you can grok chords all that well.
In time, you start building your own internalized library of "licks", little musical gestures that are automatic, and to achieve what Marc is doing, is to just string those gestures together. It sounds musically complex but when you're doing it, it almost feels like cheating, because you're leaning so hard on these "tropes" that you've built up over time.
Yeah, I just wish he'd veer off more often to these incredible improv jazz lands (like the one I posted) in his live streams. They might not be as catchy as the short loops he's currently pushing out, but damn, aren't they just delightful!
Long-time self-taught improviser here[0]. 5 years is, I think, a reasonable time frame if you're passionate. My suggestion would be to go through a beginner's course, then as soon as you can start copying and analyzing. Find things like licks and styles and little bits here and there that you like, then try to learn them by ear.
I know the "music is a language" troupe is tired, but it really does help me explain. It's sort of like muscle memory, but with a musical vocabulary.
Look up basic Chord theory, then look around youtube for theory videos on the kind of music you like. After a while, you remove thinking from the equation, and then it gets kinda hard to explain in a comment
[0] https://youtu.be/XMFnkKWXgKw?t=203