Interviewing is a crapshoot. Often your performance is irrelevant unless it's an outlier (good or bad). What you describe is why coding portions of the interview are terrible to use. Ultimately it comes down to whether your panel believes your experience is similar enough to theirs to make them feel comfortable. It's simply unreasonable to expect to be able to adequately judge the results of years of experience over the course of an hour or three or four.

Also, companies think they can afford to be selective. This tells me that companies don't actually have a development talent shortage to face, or else that they believe any such shortage is only applicable to other companies, or else they vastly overestimate the appeal they have to the labor market.