I would definitely agree with your point here, if it weren't for the wildcard option. While I think its a sad state of affairs that most devs don't know anything about how the DNS works (which is sad cause its wayyyy more simple than HTTP(s)), I agree that its often the case. That's the reason for the wildcard option! With it, large custodial services don't need to know much about DNS, they can add one wildcard record and handle the rest at the app layer. Anyone running a solo name resolver can similarly just add one record, so its all pretty easy.

I assume you saw what a, b, and c referred to :) They're pretty important properties.