I think it actually is even more relevant today than 10 years ago, as the only real production use case I can imagine for it is specialized industrial software written only for XP that no one wants to update to w10 because of the risk of breaking production but which are running on a not supported anymore OS full of vulnerabilities. If really ReactOS achieves parity then that's a possible niche.

When was it relevant?

Same as Haiku

Considerably predates it I think. I’ve followed ReactOS on and off for years, since the early 00s.

Looking at the website, they celebrated their 30th anniversary recently which is pretty impressive.

[dead]

Drivers exclusive for Windows.

You know your old Soundblaster AWE64 Gold, with all bundled programs [0]. Or that very special Analog Video grabber card you have.

Wine is user space. This is the full OS.

[0] Ok, that maybe works in linux, but you get your point.

Not yet but it seems like they've finally started working towards that. Driver compatibility has improved dramatically over the last few years, for one.

Last i tried it a couple years ago, it was basically impossible to install natively. (On basic intel haswell system)

As someone who very much dislikes the Linux/Unix philosophy, I'm happy to see diversity.

You mean Windows subsystem for Linux.

Having a full Windows desktop with a Linux install saves me from formatting and partitioning into yet another installation mess that Linux still has and choosing a distro while not messing around with display managers or searching around why some apps do not display correctly when connecting to an external monitor.

The best Linux distro is Windows (with WSL).

It never was supposed to be.