Both the black box or the awful duckface.
God
To think it's post "my god I need to improve what I do" Braindrop moment of clarity... And I'm not talking about the black box.
Seriously though, as someone who doesn't self-insert, as long as the MC looks relatively normal and age appropriate, it doesn't matter too much to me
And as someone who sometimes self-insert I would answer more or less the same.
I'm past 50yo, so there's what, one game out of thirty that have a MC that would more or less match me ? I learn since long to adapt. I'm not a student, I don't live with my family, I'm not a space pirate, I'm not a comput... Oh, yes, I'm a computer guy, but it's probably the only time the MC match with me.
Whatever one do with his game, the MC will probably never match the player at more than 50%, so personally I wouldn't bother too much with that.
If really OP is bothered he can try to limit the moment when we she MC, but just this, limiting, not totally removing it.