As someone with ADHD as well I can relate. The way I “trick” myself into working on things is to tell myself I’m going to fix a small bug or work on the terrain for fifteen minutes. I’ll look up and a few hours have passed. I think the hardest part is just getting started so if you set a small goal to accomplish then you’ll be in it from there. Everyone has their own quirks though so you gotta find what works best for you.
As for engine swapping, I personally love unity since it can do a LOT. Swapping from something as accessible as rpg maker can definitely be daunting though and you’ll have to learn a new language. Unity does have something called playmaker though, which is visual scripting (unreal has this, it’s called blueprints). There’s the store you can access for art stuff if that is not your jam.
A while back I made a post roadmapping a way to get in to unity if you want to check it out.
So you want to make a game but don’t know where to start…
Hope it helps and good luck with whatever you end up working on!