Some should quit, certainly. I'm not saying there isn't an oversupply.
That doesn't change the fact that people who are paying up to $60,000 per year for an education should not be having classes taught by people who can't hold office hours because they don't have an office.
The demand for college education at all levels is the highest it's ever been, it should follow that the demand for professors should be high. Instead universities are charging premium prices and delivering a substandard product and administrators are pocketing the difference.
We're not talking about making a cheap cell phone and some of your calls get dropped, these institutions are charged with advancing and proliferating all human knowledge. It seems like the sort of thing we should care if they do a good job of it.
Just because they want it does not mean that they should get it. This is like taking walk on roles as extras or bit parts in Hollywood and complaining you can't live on it. The world is saying you aren't going to be a professional actor.
Worse, tenure track positions aren't very rarely hired from adjunct ranks. So doing this isn't really increasing their chances.
The answer to this problem is for these people to come to their senses and quit.
>The flip side of there being an oversupply of newly minted PhDs is that there must be a commensurately high demand for PhD-level courses. What's filling that demand when the university refuses to hire full time professors?
PhD's don't typically have a lot of courses and they typically go to school for free.