Honestly speaking, I find "Win95" look and controls much more intuitive and easy to use.

The glorious days before flat ui

Flat can be fine with shadows (though if it has shadows is it flat?) and other hints but yes I think the desktop UI in particular reached it's peak with Win2k, everything since has been different but not better.

These days I use XFCE with http://www.noobslab.com/2016/03/vivacious-colors-gtk-theme-s... and it's nice.

Nope, those look much better. I guess just...don't use the widgets.

I'm fairly sure it's the same widgets, just with a better theme overlaid.

No, it's Qt Quick vs. QWidget. QWidget was created in the pre-mobile days, and while still very useful to make high-quality work horse desktop apps, the mobile platforms are much better served by Qt Quick in terms of theming, animation and touch support.

This fragmentation is frustrating sometimes, but in the end what counts is whether the framework has solutions to your problems, and it usually does. (Meanwhile, Qt Quick is improving on the desktop over time.)

This is why on an application I have done back in the 5.3 days, I decided to throw Qt away and rewrite it using standard C++ for the logic, with Java and C++/CX for the UI.

I was much more productive and I had much better integration with the respective OS APIs.