I have said it elsewhere on this forum. Instructor SEP/MEP or bashing the circuit doesn’t necessarily make a good airline pilot.
We had a 10 year SEP/MEP instructor join my last outfit. Lovely guy and could fly the aircraft fine but operating on the line apparently he was down right dangerous. He got given 3 chances at final line check and failed. Bye bye. His landings etc were all ok but just couldn’t grasp airline flying. I never flew with him but spoke in crew room and all the line trainers said they tried so hard but the penny wasn’t dropping.