The usefulness is in saving time boilerplating, plus figuring out tests I may not have thought of.
But I do closely review the code! It turns the usual drudge of writing tests into more of a code review. Last time I did it it had some mistakes I needed to fix for sure.
I'm not disagreeing per se, but in my experience my tests are so disposable they're never worth investing that much engineering effort in past getting them to pass