For what it's worth, you can still run an XSL processor as a static generator. You of course lose some power like using document() to include information for a logged in user, but if it's a static site then that's fine.

Users don't log in to my site.

I eventually started using server-side XSL processing (https://nginx.org/en/docs/http/ngx_http_xslt_module.html) because I wanted my site to be viewable in text-based browsers, too, but it uses the same XSLT library that the browsers use and I don't know how long it's going to be around.