Having had taught in several universities in several countries, son, this is indeed an issue. Most professors don't like to teach. They prefer to research. The boring job of teaching is frequently pushed on to adjunct professors or doctoral or postdoctoral students. You yourself have been undergoing this phenomena.
Personally speaking I think academic staff need to do all three activities ideally, research teaching and administration. But what happens if that as usual specialisation happens. Some people do more in one area. And as economics will predict, their earnings will differ.
And yes people pile into doing a PhD without thinking through the implications. If you do a PhD from a good school and in a good area then you're good. But think about it. I'm embarking on a history PhD. If I'm lucky I'll get a job as a school teacher. Forget teaching in a university. Even on an adjunct basis. How many students want to study history eh? So sadly, this area is suffering. Finance. Mathematics. Economics computer science all top of the heap.
Anyway. We are but the choices we make son.
National Adjunct Walkout Day: Should We Feel Sorry for Adjuncts?
Thesis: Adjuncts are victims of their own bad choices.
Caveat: Universities are run badly. Brown was run like the Russian government, and Georgetown is run like the Catholic Church. Universities suffer from a wide range of public choice-type problems. I mean it. I’ve even given public lectures (e.g., at a SUNY school last month) elaborating on the what and why of their persistent wrongdoing and mismanagement. Everything below is written with that in mind.