I don’t think anybody is complaining about the initial barrier to entry. These interviews would be more like asking a surgeon who’s worked for 10 years in one hospital to pass an anatomy multiple choice quiz when transferring to another hospital
While it's true that asking an experienced surgeon basics of anatomy is worthless, please take into account that all surgeons at least operate on humans. If you take 10 random developers, chances are most of them worked on completely different levels and domains throughout their careers (e.g. embedded dev, backend, frontend, devops will have vastly different skills).