OK, but please don't do what pg did a year or so ago and dismiss anyone who wrote "delve" as AI writing. I've been using "delve" in speech for 15+ years. It's just a question where and how one learns their English.
It really made me uneasy, to think that formal communication might start getting side looks.
I could see arguing that starting a sentence or paragraph with "Therefore, " repeatedly in one essay is empty but tbh your teacher just sounds jaded.