I'm a mediocre butler at best
Why do you think you're only mediocre?
I don't feel I am perfect at it.
If you try you best you should not put your self down. If you practice a skill you can become better at it.
But I'm bad at it and I'll never be good at it. I'm pretty mediocre.
I don't think you should doubt your own abilities like that. And I think it's important that when you feel you suck at something, you work towards getting better at that thing.