When I used to use TeXmacs I would have annoying glitches to the point where I just called back to TeX with regular Emacs. I think its general clunkyness really held it back. The problem now is that people still use regular Emacs and share the TeX file locally or use a service like overleaf that allows for collaboration online. TeXmacs in my opinion tried to solve a problem for a small subset of users that it didn't really catch on.