1.) Mirio was born with a Quirk that literally broke his own Father and his dreams of becoming a Hero because of how impossible it was to master. His Father passed down a Quirk that could kill him upon activation. As a child, he could have died each. time. he used it. Compare the millions of times he's faced literal death trying to get a handle on his power, WITHOUT A MENTOR or any sort of guidance, prior to even getting into UA with Deku. Now flip the difficulty level to 100 to turn that same Quirk into one that makes you a Top Hero Prospect at the most prestigious School and a hair away from being All Might's successor.
All Might said he would have given it to Mirio if he hadn't ran into Deku by accident. So all the qualities you listed as reasons Deku was chosen also apply to Mirio and he's a harder worker, with greater character that actually makes the people around him better. He makes them laugh, they look up to him, he makes them strive to be better, & even after losing his Quirk & his Father figure he's more upbeat and energized than Deku with One for All.
Mirio is a better character. Period.
2.) Asta was also born without powers in a world where even the lowliest peasant has some magical ability. In Deku's world there's still a percentage of the global population that doesn't have a Quirk. In Asta's, it's unheard of, so he's born into a worse situation off rip.
Despite this & without even the parents Deku had, Asta never wavered. Ran the fade with whole adults as a kid, chased MILF nuns, & took on his prodigal foster brother as a rival all without any abilities. He also trained his body physically to the peak in anticipation of achieving his goal and once he finally got his book, he put all that built up hard work to use.
Deku hadn't trained a day in his life until All Might handed him power.
If he had Asta's drive, he wouldn't be crippling himself because he would have prepared his body.
Try again.