I'll be happy to answer the portions of your reply that you absolutely got wrong:
"We are $21T in debt and cannot afford obligations already signed up for (Social Security, Medicare, expanded Medicaid). Where exactly would you shift the money from?"
Answer: No, what we can't afford are tax cuts that keep pushing money upwards, thoughtless spending on poorly designed subsidy models, and wars that don't end. In addition, our cost of health care needs to be completely re-done. Having said that, yes, our deficit has ballooned to a risky size, and that is bad.
Also also, running a deficit is not categorically bad so long as your economy and your currency hold a primary place of importance in the world economy and you can therefore successfully finance your debt. If you think otherwise, you do not know how this stuff actually works.
https://en.wikipedia.org/wiki/Government_spending_in_the_United_States
"Only if the government writes off the loan I just took on some land I bought. I was drunk when I signed the papers and not responsible for my actions."
Answer: Those two situations are wildly different, though yours at least has the benefit of being funny. You could potentially win a lawsuit if you brought it and successfully proved you were impaired beyond a reasonable standard when you purchased that land, and therefore get out of some or part of the obligation. But the ways in which this is different are far more instructive. The first of which is, your example is a rogue private action, it is not representative of a broad societal trend that occurred, again, due to private capture of the public interest (this interest being affordable education).
"I live in SoCal and blah blah blah..."
I don't, I live in Nebraska (for the time being). It's very affordable to live and work here, even though it is brutally cold part of the year and politically f-ing stupid in most of the state. However, I hear nothing, absolutely nothing, about things being affordable for anyone in SoCal.
The trends outlined in the below article, in my opinion, are indicative of bad circumstances, not good ones:
https://www.businessinsider.com/millennials-housing-market-affordable-rent-2019-6
Your argument smacks of the kind of ignorant talk used to put people down who want to cause systemic change (and also blaming people and refusing to help them based on that same ignorance, a-la the "welfare queen" fallacy).
I think we need to be able to agree on the problems, first: I am stating that current student debt levels and costs of education are too high, and that this system needs to be reformed.
I think you have a couple of decent points, too: UNL is still pretty darn cheap (many state schools are, if you are in-state). K-12 education does have a lot spent on it, and while I will almost always argue for more spending, it is also very true that "how" the money is spent needs to be reformed. You don't just throw dollars at a problem, you need to fundamentally change how they are spent, too.