I started in Sony Vegas back around the turn of the century and share your enjoyment of the standardized UI paradigms of professional software. It's great to be able to pick ups something like Davinci Resolve and just know what I can do and find the 10 keyboard shortcuts I want and then get to work, just because I learned Ae and Premiere a decade and a half ago.
I also share your frustration with iMovie and garageband... I can't get a damn thing done in GB and I've tried several times.
It's like the CLI: I already know exactly what I want to do, and I have an understanding of how the computer is going to deal with it. These apps feel like trying to drive a car with an iPhone app.
However, I work with a lot of non-professionals and they love these tools. So more power to them. I remember using logic back when I started 20-something years ago and had no idea baout how MIDI worked. I remember being able to actually have fun getting things done in fruity loops or rebirth. I'm glad there are tools out there which are nerf'd up for the beginners.