I would agree to see the outcry more as a symptom about this meritocratic system. I think we are at a point where new browser/rendering engines are developing like ladybird or Servo. An independent group should make sure that they will strive. Making specs simpler can help here. But I think many things are done for the wrong reasons (E.g. Google wanting to cut down cost on parts irrelevant to their income, other vendors that are reliant on them).

Last time I used XSLT in the browser was actually transforming PMML to JavaScript executable ML models about 10 yrs ago. Before that I think it was building a light weight web frontend for our SVN repo. With XML APIs replaced by json or binary formats, the relevance is becoming less and less. And in the end it is about legacy stuff only because there are XSLT compilers [0] that could fill the gap (maybe with a small web extension, that won't work on phones with native Apple and Google browsers...)

[0] https://github.com/egh/xjslt