There is a lot of misunderstanding here. I’ll comment, but I fear that it won’t change people’s minds.
(1) Tenure is not a lifetime appointment. Tenure means the university needs to show cause and follow its procedures. These procedures vary by quite a bit. Georgia’s change is negative, to be sure, but not beyond the pale. (And yes, poor teaching can and often is a reason for dismissal)
(2) University instruction costs are a small and decreasing fraction of their budgets. Under 25% is not uncommon.
(2B) The rule of thumb for a STEM professor at a tippy-top R1 is that the university’s cut of your research budget covers your academic year salary (9/11 of your salary). University cuts (“indirects”) are around 60%
(3) The choices are not Georgia or Yale. They may be Georgia and Mizzou. It is not uncommon for faculty candidates at Georgia to have multiple offers.
(4) There are more PhDs than academic positions, to be sure. But not 100x as many. A professor graduates N students in her career, only one of which is needed to replace her. N is not 100. It might be 10. One of the most prolific in my field has around 40.
(5) Getting tenure in my field takes a PhD (6 year average) + postdoctoral positions (3-6 years) + 6 years as an assistant professor. There is a pretty good track record for people to examine. I got tenure 13 years after I started grad school and this was considered lightning fast.
(5A) Is there abuse of the system? Sure is. But most of the abuse is coming from people hired directly into tenured positions, and not those who climbed the academic ladder.