The web has grown a thousand fold over those decades, in spite of no support for XSLT. No browser has failed (or gained market traction) by missing support for (or adding more support for) XSLT. It's an irrelevancy, even if you did like it once.
Lots of content was lost when Flash was removed as well - much, much more than the amount of content that will be lost if XSLT is removed. And yet the web continued.
The web is straight up a weaker, worse more closed off experience post-flash, so I'm not sure that this engenders the kind of response you had envisioned but now I'm worried about xslt.
Lots of content was lost when Flash was removed as well - much, much more than the amount of content that will be lost if XSLT is removed. And yet the web continued.