At my last job, my boss was very guilty of "At ____, we found x to always cause us problems", but he never really connected that "x" was a problem because of th

At my last job, my boss was very guilty of "At ____, we found x to always cause us problems", but he never really connected that "x" was a problem because of the context surrounding it, not inherently. We went through this really awful process of: Manager either demands or rejects an idea based on a totally different company -> I spend days/weeks proof of concepting/documenting/testing/validating for or against his mandate -> He says something like "oh, great!", and then continues to spread the mantra that x would never work for us because of previous experience. It was really tiring. Having to constantly document why a piece of technology for a startup in a totally different industry would yield totally different results than when he'd used it at a top 5 company with insane scale and a 500 person engineering team. Especially because most of his understanding was just overhearing people say certain things, so he just said them too, but didn't really know why.