Recently, I've been looking at yield aggregators again, and the APY on the page is written just like on a poster, but basically behind the scenes it's just a series of contracts helping you move assets around: where to deposit, how to swap, who the middleman is, all depend on the specifics.

Many "yields" actually come from counterparties: either lending out to others to leverage, or putting you into a pool to eat up volatility; just because the contract hasn't had issues doesn't mean the counterparty hasn't.

Some people keep an eye on large on-chain transfers and unusual activity in exchange hot and cold wallets, then start shouting "smart money is coming," but I always find that pretty funny... money moving doesn't mean you know why it's moving.
Anyway, before I click "authorize" now, I first check whether the permissions are unlimited and if the contract is newly written; even if the APY is high, I treat it as a test of my social anxiety and courage.