It is pretty much an MMORPG but IRL. Everyone else doesn't compare to MC because he's not like the others. That's why him being "The Player" gets brought up repeatedly. And from the get-go, MC himself already kinda thought he's probably going to be an "avatar" for something which is why The System always tries to make get him stronger. The lack of personality is kinda explained by his circumstances. He's pretty much just grinding dungeons to earn as much money as he can to support his family. He was the pretty much the weakest hunter ever. To get a glimpse of his personality, he'd have to be exposed to different scenarios but MC chose the dangerous repetitive grind of dungeons to make a quick buck ASAP. He didn't have the luxury to do anything else. If you did that in a game, you're as good as a bot, and that's what he did. If you read the novel, you'd understand all this, really.
The mom does get brought back up into the story; soon in the webtoon.
The demon girl, Esil I think, already served her purpose so there's no need to keep her in the story.
Only thing I agree with you is the ending. It was absolute shit. Then again, I couldn't finish reading the english translation coz the crappy formatting and terrible grammar just annoyed me so much, I could no longer immerse myself in the story.