- The UIs of the 90s were made with mice and keyboards in mind. The designers' minds weren't yet compromised by the existence of touchscreens, both on phones and Windows laptops.

- IT companies were building tools to empower users and actually competed with each other fiercely. It was important to make sure your UI doesn't suck, because otherwise someone else will. This competition required the companies to put users' needs before their own.

And tangential to that: "developer experience" wasn't a thing. Writing software was an engineering job done by people knowing what they're doing. The bar was set pretty high. Compare that to now, when it's almost encouraged to be a junior developer and pile libraries into your project without ever looking under to hood to assess the compromises you're making. And the way the code looks and builds is considered more important by many than the end result that ships.