That is exactly the same situation I was in over a period of years working in a company with someone similar. In the end I decided that I would do the best job

That is exactly the same situation I was in over a period of years working in a company with someone similar. In the end I decided that I would do the best job that I could possibly do with the knowledge I had and to hell with the over-inflated opinions of my line manager. The best seniors are those that answer questions you have, steer you in the right direction and are open to new ideas and suggestions.