Can I be a teaching assistant without calligraphy?

You can't.

If you want to be a teaching assistant, calligraphy can't be based on zero. If you want to be a teaching assistant, you must first read your own words, at least you can use a hard pen or a soft pen, both of which are the best.

Teaching assistant is the lowest rank of university teachers' titles, and it is a junior title among university teachers below lecturers.