Working in an industry a long time does not necessarily guarantee you have specific skills in every aspect of that industry. For example I worked for years as an electronic engineer in the video industry (TV's, cameras, displays) mostly in the analog video side. That didn't make me as expert in, for example digital video processing... OP, boss might have a point - While I get that this is upsetting and aggravating, you better pay attention to what the boss is telling you. The last thing I would ever want is to be a position where I was not qualified for my job - That leads to dissaster.

maybe your boss is jealous and is trying to mess with your confidence because he's afraid you'll get his job.

“You oversold this company as a great place to work”