i do think danny has a tendency to be oblivious but i also think he actively chooses to be oblivious most of the time.
in dannys mind the portal accident was Not That Bad. what do you mean he died? he's literally fine and right here. nothing happened it was just weird and then he got cool ghost powers.
danny knows that he cant just abandon his friends to deal with the aftermath of a fight, that it makes him inconsiderate, but he's already so weighed down with fighting ghosts in the first place and he knows that sam and tucker will deal with it so he just.... disappears after the fight is over. he pretends not to notice his friends frustration. sorry guys, he'll try to do better next time.
he knows that sam has a crush on him. but he doesn't really want to think about that right now. so he pretends not to pick up on anything. isn't he just so bad at noticing how people feel about him?
choosing to give up his ghost powers and try to be a normal kid an opportunity for less moral ghost hunters and unfriendly ghosts to take over amity. but he really, really wants to just be a normal kid. so it's it better to pretend he doesn't know about the consequences?
his parents are trying to kill him but it's really not that big of a deal. vlad's obsession with him isn't that creepy he's just a sad lonely old man. he knows that the situations he ends up in are deadly and terrifying and traumatizing, but it's it so much easier to pretend that they're not? that he can laugh his way through with sarcasm and corny jokes and brute force? repression has worked out for him so far, so why bother changing his strategy? he can just keep choosing to be oblivious so that he doesn't have to face reality.
danny basically operates under "if i can't see it it can't hurt me" logic