Chrome mostly can do anything Firefox can do since removing its "legacy extensions", so Firefox has to remove XSLT too - as Google can't afford it being not helpful for tracking - and can compete only with its JS engine - so XSLT, if to stay, could in the future only be reimplemented in JS polyfills no more, making it less useful, not cached, not transparent - to let Chrome 'outcompete' others again, race to the bottom, everything looks like a nail.
Hopefully that could be enough to complete the evidence to split Google into pieces in antitrust case - or realizing that will make Google to back off ?
yet making it to be interlinked code too.. may not last, as codes like changing and finding new ways.
Fancy stuff as JS may be very useful and I like it too, momentary, when well applied, but it needs: an effort to use it, keep working, adapting, if interoperating, all specific, for the purpose - and power, can't open 1000s tabs. Different kind of being. More fun, like with the hammer for everyhthing - not shy like XSLT trying be transparent.