@desea You have to consider that this stuff is often written by male mangaka for a male audience. Your typical Shonen (the non-action variant) stuff.
That does change somewhat when you look at works from female mangaka. Though there you *can* have the opposite stuff happen.
Though that said I think the female MCs are usually better. They are not as dense.
Then there is also the typical rom-com elements which break a lot of series. but tbh I am not too much into SoL.
But yeah the whole "lets both be so dense we not talk about we like each other for 1000+ chapters" is a thing. But still better than your typical harem-stuff