my brother in christ, this literally means you have impostor syndrome.
we are all objectively bad when compared to gordon ryan. a 45 year old comparing themselves to kids who train and compete obsessively is equally silly. you put in the work and the time, the people who promoted you believe you deserve it, so you do deserve it. and being a black belt in jiu jitsu means you are objectively good at it.
i do know what you mean, i got promoted to black belt last year and my first thought was "damn, i have to be the shittiest black belt out here", i still got tapped by the young guns way below my rank. but that's part of the sport and getting older, nothing we can do about that.
congratulations! it's a big achievement and you should feel very proud!