Windows fans, like being a Mustang or Corvette fan, represent arrested development in last centuries technology...
I also don't really think computing advances in such a linear way. Lots of cool new tech is about digging up underappreciated insights from computing's distant past and applying it in a new context, or even just propagating it more widely.
I'm not saying Windows 9x in particular had anything super interesting going on. But all of the viable desktop and server operating systems are based on really old tech, and at the same time computing's distant past is full of hidden treasures.
Win9X and the VxD layer was a neat virtualization system running in a very resource-constrained environment with a lot of backwards compatibility requirements.
Oh it did though, it is a very interesting OS. Much more interesting than it usually gets credit for.
It's a proper 32 bit OS with pre-emptive multitasking and demand paging that is enough of a chimera with DOS that it still supports DOS programs, 16 bit Windows apps, and even your old DOS drivers - side-by-side with all the new 32 bit stuff.