Operating systems are cool.
Just about every popular general purpose operating system is some variation on UNIX. That is sad, just like it would be sad if JavaScript, TypeScript and Coffescript were the only popular programming languages. The only difference in scenarios is that the OS is much more significant and critical than the programming language.
Windows is fundamentally different from Linux and UNIX. ReactOS is a clean room reimplementation of that, bringing NT's many excellent ideas to the open source community. That is a good thing, even if you never get to use it. Don't forget that, just like in every other part of life, different != bad.