Beyond the obvious 'MC goes out of his way to downplay his own efforts' the author seems to bounce between two ideas over and over.
First, everyone underestimates the MC both because of his specific type of magic and because he himself encourages it. You can generally expect that he will win over at least a few people who actually understand just how OP he is. There might be an arbitrary number of people who keep their original attitude if they aren't required for whatever point the author wanted to make, with a rare chance that someone keeps a grudge.
Second, for whatever reason the MC has this compulsion to teach everyone else that even great people are still people and need support and to express their humanity. Also, being OP he might actually contribute something toward teaching magic or other principles related to how he uses barriers, but mostly just the 'think of their feelings!'
I don't know if it's maybe just related to the target audience (though some of the violence and references to death make me doubt it's for young children), but some of the dialogue and plot points come off as extremely childish to me. People act petty in the most silly of ways (although sometimes leading to potentially fatal situations). I really like some of the stuff going on here but it's hard to really love it when it can't decide how serious or mature it's supposed to be.