I actually really like the flat colors look with no gradients. Kind of like how the default web Lemmy UI is, but I wouldn’t use rounded corners anywhere. Back in the day I spent a lot of time theming my XP computer to look like this. Then eventually Windows ended up doing something similar in later OS versions. I have a tiny blog thing that looks pretty much to how I like it.

What I hated was the glassy transparency nonsense. Windows itself still has a few transparency options which I will always turn off.