Give the show one more production season.
Have the show aimed at an older audience
Make all the paladins besides maybe Pidge adults like Shiro.
Have a smaller and less bloated surrounding cast so individuals can get more focus.
Introduce Lotor earlier.
Make Keith less shit.
Combine the Galra generals into just one character or get rid of them entirely.
None of the damn Voltron Coalition bullshit.
Make the Blades of Marmora do more than be redshirts.