Windows 95 was developed over several years with a lot of research and user studies. The primary objective of all this work was so that a person without prior exposure to computers could figure out how to use it. The software was designed to help the user accomplish the tasks they have set out to do before sitting down at the computer.

With most modern mainstream interfaces, both the audience and the objectives have changed. The overwhelming majority of the audience is now computer-literate and can be counted on to figure out how to use the basic features regardless of their quality. And the design objectives for many interfaces have changed to manipulating the users to do what the developer wants them to do, with the user's tasks relegated to a side quest.

Another factor is that Windows 95 was developed for "install it and leave it" operation, with the next upgrade coming in a year or two. A lot of attention to detail was unavoidable because you could not push an update a week after release to patch a bug. At the same time, Microsoft was offering real live person phone support for its products, so every UI flaw cost them a lot in support costs.

Also, one of the design requirements was to fully support only-keyboard operation, and a lot of QA effort went into ensuring this was true. This meant that every UI element had to have a keyboard cue. This duplication of accessibility resulted in a UI which was much more thoroughly evaluated for its efficiency.

Finally, I think there was a different culture around design. I think a higher portion of people in the UI field were there for personal and passion reasons, and would have been embarrassed to have anything to do with the type of blundering buffoon of an interface that is common in today's computing.