Just out of curiosity, how much time ago did you try it? On the one hand the latest version, 2.1.1, runs very smoothly and has a complete set of features (the extensibility of course allows to augment them, just like in TeX); on the other hand TeXmacs has very different principles than any other document preparation system and need just a bit of time (far less then LaTeX) to get used to.
This blog post by Massimiliano Gubinelli may be a good introduction:
https://texmacs.github.io/notes/docs/art-of-math-writing.htm...
