Man, the idol stuff felt like a typical "Big Lipped Alligator Moment": Apparently, this world has advanced enough to have microphones, glow sticks and effing spotlights, but still uses swords and other medival weapons. As long as we don´t get more world building like "guns and other modern weapons are less effective against monsters" or "the existence of magic led to some inventions never being made", this just seems weird. I hope it wasn´t just to explain why the MC is hurting for money right now.
And I agree that Argus was quite reasonable: If all adventurers are shit, you can´t be cherry-picking about who you have in your party. And it appears that the other members of the party were much older and probably past their prime. We don´t know how much harder b-rank or a-rank quests are.
So yeah, kicking the MC out so he can actually do more with his life than be stuck with party members who might be too old to go adventuring in ten years was the right call. He could have wordeed it nicer, but in the end, he has some good points.