Fun fact: David Karp saved the world from XSLT being Tumblr's blog-theme language.
XSLT was a big part of my previous job, and I liked it. It was weird, but fit certain problems well! (Like me!)
When making Tumblr’s custom-blog-theme template system, I first implemented an XSLT version.
I showed it to David, and he was diplomatic, but he clearly HATED it.
XML is bulky, ugly, formal, and overly structured; Tumblr, and David himself, were none of those things.