I would agree with you if there was a connection between the quality of the teaching and whether or not the teacher is a professor or a TA, but I don't think there is. Professors are hired for their ability to do research, not teach. Many see it as a chore. And TAs are - in my experience - only allowed to be the instructor of record when they've been around for a while.

Personally, one of my best math teachers in undergrad was a grad student. He was leagues better at teaching than all but two of the math professors I had. I also had two TAs who ran recitation sections (homework help and extra discussion) who were excellent. The TA who ran the recitations sections for one of my physics classes was a far better teacher than the professor for the course, and I would have preferred he teach the class.

I taught a class when I was a grad student. It was a summer course on intro to programming for non-majors. My department historically asks some grad students to teach the summer classes. Several of my students told me they were thankful that they got a good teacher.