What he's saying is that he's tried later versions of the same OS and he doesn't like them.

I've tried the later versions, too. I don't like them either. As such, I think his assessment is sound.

Additionally, this piece does not stand alone. He has written about this extensively before, in January 2021:

https://morrick.me/archives/9150

And then revisiting it a month later after it received a lot of comment and attention:

https://morrick.me/archives/9220

He went into great depth in those posts. He knows this subject area exceptionally well. The first one of them, particularly, went viral and TBH I'd expect you to have known that, and to have read those earlier posts, before you start passing judgement. Otherwise you look ill-informed and ignorant, and to be judging on that basis of a lack of understanding.

In addition I'd add that I started using Mac OS X with 10.0, and on unsupported old Macs because new ones were too expensive for me to afford back then, so I hung out in various fora for people running unsupported kit.

(P.S. Don't "lad" me. I've been doing this stuff for more than a third of a century, and that's professionally, after nearly a decade as a hobbyist.)

I'm still in those fora and their modern continuations.

When Riccardo said that he felt that the experience had degraded since "Snow Leopard", he is merely expressing a widely-held view. Many old OS X hands feel that from 10.0 to 10.6 it got better and better, and since then, it's deteriorated and it's still doing so.

In other words, this is not a controversial or contrarian view.