Server-side XSLT tools have existed for 25 years or so. The people complaining about this want existing websites using XSLT on the client to continue to work without changes.
It's actually possible to support it by re-implement it by js or compile to wasm and running on client side. There are extensions to support pdf(pdf.js), flash(Ruffle), mht(UnMHT). So it should be possible to do the same thing for XSLT. The real question is "Who want to"? Does xslt have a large user base like pdf, flash, mht?
