So, the only reasonable move for an individual is, simply don't participate in the system in the first place, keep your money in the mattress. (Crypto equivalent: hold your own coins).
The problem is, credit actually creates real economic growth. A society that encourages credit via regulation will outcompete a society that leaves it to an unregulated marketplace (and thus disincentivizes individuals from participating).
Are these people adults? Yeah. Should they know better? Yeah.
The question is should we do anything about it? The Super Bowl is the most watched television event every year and there were lots of crypto ads this year. Do people need to be protected from themselves?
We have regulate the traditional financial industry. We put warnings labels on cigarettes. My view is that we need even more regulation of the traditional finance industry and apply those same regulations to crypto.
It's not a bug unless you believe adults should be treated like children and not be able to take the risks they desire or face the consequences of those risks. Anyone investing in DeFi should absolutely have known the risks; it doesn't justify giving the government even more power over people's finances.