My son had a mix of instructors, some with PhDs, some with Masters, some teaching classes at both the local community college and the university. He had one “full professor” for a math class, but that definitely did not guarantee a good math class (not all professors are gifted teachers.) One instructor worked for the university in a non-academic position but was also a PhD student, and was a nice teacher, but really had too much going in order to prepare for class each week. One science professor was retired, and brought back to teach part time, but that professor often overslept and arrived late for class. All labs were run by TAs.
When I think of universities that rely on TAs, I always think of UC Berkeley, and my son did not have that experience at all. All of his teachers/instructors/professors at UA were experienced adults, knowledgeable, and some were better teachers than others. But when it comes to college, it is a partnership, and no student should depend on the instructor doing all the work anyway. A student gets out of any class what he/she brings to it, and sometimes has to do that in spite of what the instructor brings to it. Thankfully, my son enjoyed a really good group of instructors his first year. Even the one who should have stayed retired knew his subject, and, even if he shouldn’t have been in the classroom anymore, he was funny and the class had a good time.