Regarding csl: what feature do you think are missing? If you take a look at the github repos you'll see that a lot has happened recently.
CSL isn't fully compatible with either BibTeX, BibLaTex, or even a mainstream
English-language style like the Chicago Manual of Style:
https://github.com/citation-style-language/styles/pull/4578#issuecomment-593047568
So, I join everyone in strongest applause for pandoc going its own way.