You definitely can't trust people's self-evaluation either way. Lots of really skilled people are self-critical. "Reading people" of course helps but it is now

You definitely can't trust people's self-evaluation either way. Lots of really skilled people are self-critical. "Reading people" of course helps but it is nowhere near enough. But you don't have to become an expert. If I hire a plumber or carpenter, I cannot do what they can. But with enough work I can understand which plumbers or carpenters will do a good job.