they weren't promoting an OS, they were promoting a user experience - A GUI that competed with the Mac.
There were OS improvements too, but I have forgot what. The real improvements came with Win2K - one of the best versions of Windows ever.
I don't remember if Plug-n-Play shipped with the original Windows 95 (it's certainly there in the final OSR), but that was a pretty big shift from the manual IRQ and port mapping days of DOS/Windows 3.1.
IIRC we got long filenames with Win95, and a built-in network stack, no more Trumpet WinSock. And it did seem more stable, not nearly as good as NT/2000 but better than 3.1.
Win2K was my favorite as well. The transparency was tasteful. Everything worked and for the most part didn’t crash. Many (most?) games worked. It ran great on a PIII 600mhz. Everything good about NT4 was better and most of the consumer friendly stuff starting to take shape. The disc was even gorgeous. Peak MS design and engineering.