I don't disagree that there's no development methodology that can "prevent" technical debt, poor documentation, etc. That's not a reason to use one which directly encourages it.

I think you are misunderstanding an important point here - Agile is not done badly just because people don't understand how to do it properly. It's done badly because it is profitable in the short term for companies to do it badly.

Making your workers super flexible, able to respond to any change, etc - in every industry this works great in the short term, it looks like your company is doing super well. Then your workers burn out and the disaster begins. It's no different to running a machine all day in a factory with no maintenance; you save maintenance costs now, you cause huge ones later.

Agile, unlike waterfall, instructs people on what should be prioritised in a project. Those priorities all serve short term interests - and in a world where companies are judged on a yearly basis financially, there is every reason for them to use Agile knowing that it will look good now and someone else can clean up the mess later.

As such, you can't argue that "all methodologies have this problem", because other methodologies don't tell developers to prioritise commercial considerations over development practices.