Same here, the OS nerd part of me misses the heterogeneity of computing systems, before it became UNIX/POSIX vs Windows for the most part.

Now with WSL and its use being increasingly relevant (MXC, Windows Server 2025, Windows IoT Enterprise), Windows is increasingly looking just like DEC, IBM and Unisys mainframes (microcomputers) with their UNIX subsystems[0].

So we really need new ideas in OS space.

The mobile space has some alternative approaches, however it is mostly replacing userspace, while keeping an UNIX kernel underneath.

[0] - Yeah, Windows NT already had it somehow, but we all know how little effort that was.