I'm not lamenting it being removed.. but will say that it was probably a huge multiple more popular and widely used than XSLT is in the browser.

I'm genuinely curious about that. But, this says a lot more about how different these standards are. FTP really needed a good successor, which it never really got. So, there is a strong use case, but technical deficiency to the protocol. So, FTP was overcome by a meriad of web forms and web drive sites, as a way to fill the gap. Still, resumable chunked uploads are really hard to implement from scratch, even now.

Dropping XSLT is about something different. It's not bad an in an obvious way. It's things like code complexity vs applicability. It's definitely not as clear of an argument to me, and I haven't touched XSLT in the past 20 years of web development, so I am not sure about the trade-offs.