If you're mediocre in a statistical sense (i.e. being average), that means that you're better than half humanity.

Not too shabby, isn't it? ;-)

It's a matter of perspective.

Jokes apart, I know your situation. I too suffer from depression and lack of meaning. And yet, even if you're average, you could still give your small contribution to the world - and the world would be a bit less without it.

E.g. if you were somehow of a father figure for that kid, maybe you do not realize it but you probably have made an enormous difference in his life. Without you, he might have felt lost and scared and helpless.

You know, oftentimes society make us think that we are meaningful only if we do great things. But this is a lie: we can be meaningful even doing small things.

Try watching "It's a Wonderful Life" (1946): https://www.imdb.com/title/tt0038650/

Maybe you matter more than you think. :-)

Maybe the belief of your meaninglessness is a delusion (depression usually makes one believe untruthful things).