@jk I'm a nerd who agrees with despite my different background with the PC.
I started with DOS which meant a command prompt and whatever GUI I landed on was wildly different from program to program. Then Windows 3.x "standardized" the look of programs and by the time 95 showed up I remember being somewhat disappointed because the new button design was less chunky and I liked the big round rectangle look better.
My first experience with online services was with text based BBSes - just text and ANSI art made by underground hacker types and underaged wannabes who put a lot of effort into pushing a limited medium (extremely limited compared to DOS games) into looking as wild and personal as possible.
So when I started using the web it was as underwhelming as you describe it - basic, simple looking web pages without the solid feel of a DOS or Windows program or the odd and underground artistic designs of BBSes.
Even when HTML capabilities improved something felt off and not quite right. I hated flash sites and the artistic sites that made it difficult to navigate - I expected a document and instead started getting lost in incoherent UI mazes. Turns out that while BBSs were also wild and artistic they mostly followed a UI design formula where as the web at the time was still evolving so everyone was doing their own standard.
And then native applications started mimicking web design, occasionally done as an Internet Explorer embed. And webapps happened and it all felt wrong for the same reason you're describing.
I think the other reason I hated Windows 8, beside them trying to kill a perfectly usable design in favor of something that belongs on tablets instead of PC, was that their new 'flat design' looked like a corporate website instead of an operating system. No more chunky clicky buttons, no shading of light on windows and widgets to make them feel present. Just basic square bars and crude, simple icons thrown around with lots of whitespace for touchscreen finger taps that weren't going to happen.
That feeling hasn't gone away even now with Windows 10, 11, and modern Gnome on Linux, and even KDE somewhat.
Today everything is a 'website' even when it's not and it all just feels wrong.