They only show the good part of 90s UIs, the standardized part. They don't show the part where every installer wanted to look unique, weird ICQ clients.

That was every installer looking unique now it's every app wanting to look unique.

I don't do much with Windows nowadays, but I do touch it from time to time and I don't think much has changed in this regard. Off the top of my head: driver installers for Intel, Nvidia, and Brother printers all look unique. Same with the installers for Firefox, Chrome, etc. The MSI format has brought some standardization, but it's a fairly rigid framework that leads projects to building their own installers.