I've never seen this article before, but it does not read like a polemic. Do you know of a rebuttal of the points mentioned?

So what if it's written by the author of a competing tool? Can you show that it's actually wrong instead of dismissing it as a ‘polemic’?

"Competing" tool - I suppose, but an open source, free tool. He doesn't have any skin in the game.

Describing it as a "polemic" seems like an overly emotional reaction. Did you actually read it? It seems a well-researched, well-informed article to me, with solid verifiable facts.

The only experience I have had with xz is uncompressing Apple’s Xcode archives. All I know about that is that it takes forever to do some sort of useless “signature verification”.