Windows is a good product but not perfect. Otherwise someone would topple it. I don’t know why it’s so popular to slam products that are used so widely. Just counter culture warriors if you ask me - too cool for school.
No, there have been dozens of much better products, Like Atari GEM, Geos, Tripos, Borland, QuarterDeck, TopView, OpenLook, OS2, etc., but Microsoft illegally attacked and destroyed them.
Illegal methods were used like buying up shelf space, forcing manufacturers to by a MS OS for all computers they sold, IF they wanted to be allowed to by any MS products at all, etc.
As to what is wrong with Windows, it is fundamentally the least innovative, with ancient relics that were never ready for prime time.
For example, most people do not realize Windows actually boots into DOS, and that loads Windows and then switches over.
Another problem is COM. Most people don't know or care what that is, but its Microsoft's way of having one program call another.
And the problem is it by-passes the initial code a program would have, and instead allows remote access of individual C++ object method calls. That is incredibly insecure. It prevents any Windows of ever resisting any well done attack. Your network card then can totally make the computer totally change files or anything else it wants to do, and you can't stop it because there is no way to know.