Is There a Monoculture in Operating System?

We've kind of in a bunch of different ways, let ourselves get into not quite a monoculture, but pretty close to it for a lot of different things in our whole tech stack. And I think that's something that we kind of lost from the original internet where there were always seven different options for every part of the stack. Now almost everything is down to just one or two protocols from one or two providers. But you don't really have any other options in operating system either.