Minimal "flat" UIs are possible for normal people to implement. In the 2000s I had no idea how I was supposed to make a button that looks like it's made of drop shadows and fine Corinthian leather for a project in my free time.
(For that matter I don't know how I'd get it done for a professional project either.)
I was right there with you. I was very supportive of the improving app UI standards at the time but it started to feel like a contest of whose design has more visual complexity and nuance vs the real usability.
Windows Phone in particular was a huge breath of fresh air for me (rip) and Material Design a welcome evolution that I still feel strikes a decent balance.
(For that matter I don't know how I'd get it done for a professional project either.)