It's a lot more basic than that. Everyone can steal game knowledge by just copying what other people do, but the ability of progamers to click quickly and accurately and efficiently divide their attention and context switch between multiple things is way harder to copy. If you've never seen the first person view of a Starcraft 1 progamer, you should watch this: https://www.youtube.com/watch?v=JfAU2lw6BrQ#t=6m8s

It's the same with FPS games. Top players easily spot the tiniest movement, have really fast reflexes and are good at tracking. This transfers between FPS games.

For sure. I've been casually playing RTSs since starcraft 1 (1998ish) and love RTS to this day even though they've slowly waned in popularity as consoles took over. Most are very similar especially in fundamentals. Gather resources, build, expand, and push. They usually just have a different coat of paint of it. What rules supreme in all RTS are the APM (actions per minute).

I'm bummed we don't have more of them.

I'm trying to follow the transition of Beastyqt from SC2 to AoE4, and they are very different games. I still don't understand AoE4 to well, but IIUC in AoE4 there are no nukes that destroy your whole army in an instant, so you must watch every single army continuously to avoid traps like in SC2.