[generationP]

There are lots of things that are worth improving.

The lack of accessibility features (structured PDF, alt-text), or more precisely the glacial pace at which they are getting developed, is grating. In truth, a well-written TeX file is itself accessible in most reasonable senses, but not everyone posts TeX sources of their work. It reminds me of the early 2000s when making PDFs was considered high wizardry and everyone was dealing with half-broken PS and DVI.

Better tables would be nice, but it's not clear what a perfect support for tables would even be. Unlike HTML, TeX has deal with page size limitations, and it's far from clear how tables should adapt to those.