I think Joss Whedon gets more praise than he deserves.
I mean sure Buffy was good. Wouldn't put it in the realm of classics.
Firefly was... not really original. The mashup was new but it was pretty much not that interesting for me. Star Trek with Space Cowboys and bounty hunters.
What little I've seen of his other works I have basically been "😐"
I think he's popular because he's average movie director quality on TV and that's rare.