I mean, multiple people have tried multiple times and he refuses to believe it or accept proportionate compensation, and there's a succession conflict going on in the background of the kingdom, so the premise has been that the fewer people know about the absurdly talented Innocent Little Guy who hangs out with the princess that has an active plot to assassinate her going on, the better. Loose lips sink ships and all that.
Look, I'm not trying to start shit with the comment section, but "comically" slipping and/or shouting "it's impossible/not normal" at him isn't exactly "trying to explain to him". You say he refuses to believe....well, duh...he's from a village of overpowered weirdos, he legit thinks that everyone can do what he does, because until not long ago, everyone around him could do it probably even better than him.
Maybe I'm failing to explain myself better, and I understand this is part of the plot, but reading of Yurishia's guilt of not telling him things properly because she and everyone else think it's better and safer for him it's starting to feel like author just can't write character growth and prefers to stay to the "safe" comedy of "op but dense/dumb character".
Sure , let's keep the op dude skills a secret from the dude himself meanwhile he goes in the middle of the town, digs a hotspring and builds a footbath in a couple of hours like it's the most normal thing in the world.
I know it's me and maybe a couple of other people here that think of this, but making it so that Kuruto becomes aware that he can do things that normal people can't, won't ruin the plot.
You can still have people going after Lise's life, people trying to summon demons, political shit and overpowered creations.
What would change is simply going from "look, Kuruto made me this sword...oh shit, it's a holy sword, wtf" to "K: i made you a sword that has the same functions of a holy sword" and people going ape-shit about it
Besides, considering how many people already know about Kuruto's abilities, I don't understand how him knowing and becoming aware of it would bring a loose lips issue.