The feeling of being `mediocre` really bites

I started the startup journey about 2 years ago after working ~18 years in big corps, have built 2 or 3 products along the line, I have good endurance, I love the things we are working on, the team is great, super talented and wonderful people. Sometimes, the feeling of "mediocre" really bites me, the feeling makes me drown in the darkness that denies myself and denies the products to be meaningful, when that feeling comes up, it is really depressing, it feels like we can never make something that really matters, not having a bit influence on the world, not to say "changing the world". I believe there are many founders, adventurers here, I think everybody is different, how do think about these negatives?