I'm sure there are plenty of problems with the open web, and that Google is not entirely a stranger to them... but removing an ancient language that basically failed to get traction is not one of them. No matter how elegant and advanced a certain class of nostalgic XML programmers find it.
And no, XSLT doesn't have much to do with how much RSS thrives or not. RSS is basically consumed by RSS reader backends, not directly by users on their browser.
One of the web platform's problems, is that it accumulates untold cruft from every failed experiment. The entire XHTML exercise turned out to be an expensive mistake, but we can't remove that because too many pages depend on it, and it ended up in a whole lot of places, including the EPUB definition. But at least XSLT could get removed. Yay for that.