I have a few questions.
How would you think of the story if....
Deku beat Todoroki?
Deku beat Stain?
Deku won the sports festival?
If he didn't get OFA?
And most importantly
If he was born with a quirk?
Unlikely but predictable because
protagonist, more unlikely but predictable, predictable, without OFA I don't think we would have got a story about him?, and for the last question, there is the spin-off "Vigilante" that, even if I didn't read it, I think Deku would have become if he had a normal/weak quirk.
The reason why I think stories with "underdogs" will always be popular is exactly because that character is relateble, and it is a good thing; I honestly can't feel empathetic towards someone OP who lived for 3000 years because I know they will succeed. Meanwhile is not because Deku has a shitty writing that we enjoy when he fails, but because we can see our own failures and it will be all the sweeter when he'll finally win because actual growth can be seen. The fact that Deku fails is realistic, and your first three question are what kept me reading the manga, because for once I was "Wow! this character is not receiving all the things he didn't have at the beginning, he is still struggling, but he is improving even if it's not clear to the whole world". Sure, we know that one way or another he will still succeed, Horikoshi made it clear from the beginning and honestly it was a smart move, because it's not a false "Will our hero do the thing? OOH HOW UNPREDICTABLE HE DID IT" but a "He will do the thing! Watch his journey and his growth!". This is to say that Deku and Naruto don't really have something in common, the latter fits the sterotipical shonen protag meanwhile, as someone already said, Deku does not.
I'm not head over heels for Deku but I like him because I don't think he's boring, he just has some character traits we are not accustomed to see in the main character, and this is surely a good thing.