As a 21 year old, I don't see how you could try to go indie with a family and mortgage.As a seasoned developer with a family and mortgage, I don't see how you could go indie as a 21 year old. Your probability of achieving absolutely nothing approaches 100% (and the end result may be career damage that will carry through for the rest of your professional life).
This story really has nothing to do with the fact that the guy has a family or a mortgage, and exactly the same realities apply to a 21 year old with rent and car payments. So it's a little humorous seeing every 21 year old (speaking of many if not most of the comments on Reddit) trying to declare that his core issue, which is really wishful "it won't happen to me!" denial. If anything, the guy with the mortgage and family obligations should have the motivation to achieve what is necessary, whereas this guy seemed to make horrible choice after horrible choice.
The story here is simply that he had a gross inability to estimate (if, as his runway comes to an end, he has so little...wow). And despite the fact that you disparage 2d platformers and Unity, the reality is that Unity, for instance, does a dramatically better job as a basic engine (for essentially all sorts of games) than the overwhelming majority of developers will do on their own - if you aren't John Carmack, your probability of doing something better is incredibly unlikely.
This isn't about pride (oh, boastful "I'm too proud to use that..."), it's about raw stupidity. It's building your house by deciding that you'll first make your own drill because surely you can do it better than DeWalt. Starting your web app by first making a custom web browser. It is project planning and introspection gone perilously off track.