First: nobody is forced to get a graduate degree. In many fields (like programming), it's nothing like a requirement to earnings maximization. Since grad students already have degrees, they are also free to work and save until they can pay for fees outright or reduce their loan burden.
I don't have total stats in front of me, but it looks like the Law/Medical/Business schools are ~50% of graduate employment at Harvard. Take it as read that these are worth borrowing for.
The other 50% -- AFAIK there is a significant portion of students on fellowships/scholarships of some kind. My guess is very few people are taking on a bunch of debt for a Divinity PhD.
At this point, it's fair to say that Harvard offers better financial value at all levels for its programs than many public universities offer their in-state residents.
It's interesting that so many replies function on these kind of assumptions when I am telling HN my literal experience at an Ivy League postgraduate program. I received two of the available three fellowships one could compete for. They covered less than 5% of tuition overall. Six figures of debt was the norm for my program.
Now of course, as you said, no one is forced to get a degree in humanities or what have you, but my point is that if you make expertise in these fields contingent on massive, insurmountable debt, you impoverish the culture.
You've hinted at your experience without providing details (even the school or the type of graduate program). I obviously can't comment on your situation because I know nothing about it. I am literally assuming nothing about your experience.
I do know other Harvard grads (both undergraduate and grad programs) and have some insight into their situations. They don't have "massive, insurmountable debt." Anecdata abound.
I vigorously agree with your last point.
All that I said I do agree we shouldn't be burdening our youth with crippling student debt. But the idea that our culture comes from our humanities departments seems a little absurd and not supported by evidence.
As a result the people I know from the time who went on to graduate degrees all had free rides (except the MFAs, who I admit are a mystery to me, and the people who went back for MBAs later).
There are also fields where a doctorate is the entry level qualification like biotech, materials science etc. even in the private sector, but that's what happens when a there are more than ten times as many PhDs producer as there are academic jobs for.
However, it's a long slog without a big money payoff after graduation, in fact it is better to be a student in most cases.