I shoot with 2 of my wife's cousins. One is a former marine with 12 years as a range instructor. He was blown away at the performance of my first AR build, especially since I had only purchased my first gun ever 4 months prior. Now, he taught me a lot about shooting technique and helped me improve immensely.
The other guy was in the Army for over a decade and constantly makes a big deal of my "gun knowledge", but the fact is I only know a lot about a very narrow slice. But I also don't care about most of what I don't know. If I find a hole in my knowledge base and it's on a topic that interests me, I'll make myself enough of an expert to master just that aspect.
I still listen to anyone who has an opinion, because I'm always refining what I think I know. But I didn't need someone to pre-chew my food for me.