If you aren't a professor and you are teaching classes you are an Adjunct/Lecturer which is a dead end career-wise. Maybe nice as a side gig or when you retire but a horrible position to be in otherwise.

Edit: I actually don't know what you are arguing, I think the point is that you won't get a job as a Professor without a PhD, getting teaching offers is completely different and happen to people in industry without PhDs all the time.