I think your post is very much the core of adult learner improvement and I wish we could pin it up should be taken to heart by most people who are trying to get better, almost religiously. Being able to get more spin and vary your spin increases your options beyond what is immediately obvious. I like the way you call it spin supremacy. If one is complete, there is probably a speed/power element to increased spin as well. But that would dilute the message and make it far less useful.I don't have the benefit of a robot or multiball so all my practice is from actual scenarios in hitting with human opponents, so for me the transition was quite natural. I had to substitute it with a lot of shadow practice in front of a mirror instead.
On shot stability, I saw a clip by Zhang Jike sharing how he practices. He says that he mostly practices a lot of late timing loops, done with as much spin and feeling as possible. This is something I always go for in training too. Imo once you have extremely good feeling on spinning the ball your consistency will skyrocket, because of the added safety margin that the Magnus effect adds, and also increased spin production means it becomes easier to override the incoming spin of the ball which means there's less need for angle adjustments. Also taking the ball late allows you much more room to actually look at the ball, decode its trajectory which increases consistency significantly.
What I noticed in my own journey of improvement is that there's a concept of spin supremacy - when I level up it's mostly because I'm producing and controlling increased amounts of spin. If you have "spin supremacy" over your opponent it becomes quite easy to win because you can handle their spin easily while they can't handle yours. If they have "spin supremacy" over you it becomes a very hard battle where you struggle to even loop their heavy pushes and their serves, and when they loop you can't even control it because it's just too spinny.
I remember when the new plastic DHS balls came out in 2017 and it was obvious they spun less and people thought Timo would struggle. Then he actually went out and won the Korean Open if I remember correctly. And they asked him about it and he just said he traded winning with spin with winning with consistency made possible by spin. It really is easy to underestimate the possibilities that enhanced spin opens up to you