> If that were to be sustainable you would have charge higher interest on the loans then you give to savings.
Which is exactly how protocols like Compound work, although 'governance tokens' are also issued simply for using the system.
> These DeFi yields must be funded in other ways than just loans.
Which? DeFi stands for Decentralized Finance, which pretty much means the rules are easily available - as long as you talk about a specific example, not spherical cows.