Eh, this MC is garbage. He knows the weakness of his style, but he doesn't even try to explain what he is doing. I mean, how hard would it be to just tell them to have a go at a dungeon with him not casting his magic and with him casting it, as a practice run? Then they'd see what he is providing. He could also discuss with them how best to use his powers, rather than him just reading everyone's mind and doing his own thing. Then they could also discuss a strategy for the viewers to like him, because after all this is entertainment and even if he is competent, if the viewers don't like him they're stuck. This is an extremely competitive world, is he not going to be motivated unless everyone is kissing up to him?
I can see how it's going to go too, the demons are going to kiss up to him and praise him without him actually doing anything differently, because they were on the receiving end and know what he has been doing. The party members were rude, sure, but they're actually motivated people with a goal they want to achieve. It's just that they believe he is in the way of them achieving their goal, and he makes no effort to correct them. Even if he was obviously contributing, a gloomy and passive guy like him doesn't make for good entertainment. He hasn't shown any motivation, even though he has the backing of the strongest member of the party who believes in him and knows how much he is adding to the team.