The only currently existing purpose of those things is to trade scam tokens for other scam tokens, which makes them effectively meta-scams. What I mean is that, like Ethereum, they're not scams in itself, but their only real-world use-case is to provide a decentralised platform on which to run scams.

Lazy and shallow take. But at least those using the “scam” DeFi protocols still have custody of their assets, which is not the case with FTX depositors.