Yes, that OS. There is more to an OS than technology. Mac OS X was the technological solution they needed, but it has ALWAYS been an inferior UI. Many hundreds of thousands of words have been written on this.

If you're at all curious, you can start here [1] with John Siracusa's famous piece on the Finder.

[1] https://arstechnica.com/gadgets/2003/04/finder/

I am into computers since 1986, and the first Mac I touched was in 1994.

Speak for yourself, then. I can tell you countless people used to find computers easy to use when they had Macs in the 90s. Now they find computers baffling and want essentially nothing to do with them.