Most of the world is powered by Unix (and its clones/derivatives), at least in the infrastructure space, with a small percent still running Windows Server for some masochistic reason. Outside of playing with OpenVMS exactly one time with qemu (purely because I kind of liked their goofy shark logo [1]), I've never used anything from DEC, but throughout the 80s my understanding is that DEC was a force to be reckoned with. I think there was probably more diversity in operating systems back then.

The DEC stuff was huge for a period of time, and I feel like there's an alternate universe where VMS and VAX stayed the standard, and Unix is the footnote. I'm not sure that universe would be better, there's probably a reason that Unix won overall, but it's not like DEC and VAX were tiny things.

[1] https://upload.wikimedia.org/wikipedia/commons/7/72/Dec-vms-...