Morty gets terrible grades. Morty is book dumb, and a lot of the scenes calling him out as dumb reference his grades or schooling, especially early on.

Morty also travels the universe with his high-scientist drunk-ass grandpa, and can fix or rebuild most of grandpa's stuff from scratch, but he doesn't understand it.

Evil Morty is able to take over the Citadel.

1 - Morty is book dumb. Don't ask him for chemical symbols or math

2 - As of the story we see, Morty is essentially technician level to Rick. He shows flashes of being able to do more, but he is both missing a fundamental education and specific knowledge that Rick has.

3 - The one thing Morty does understand is Rick, he makes that point pretty clearly when he's disarming the neutron bomb in Evisceraters. Give a motivated Morty a planet's worth of Ricks to manipulate, and you see where we end up.