Maduro refused UN aid months ago because the UN refused to let him distribute it and claim credit / keep people opposed to him from getting aid.
He's always been opposed to receiving aid, which is why the introduction of American aid at the border is not a mere humanitarian effort by the United States government, but a provocation.
The people in the streets of Venezuela need the aid, if Maduro is rejecting it, that's him being his usual self-serving self, but don't try to claim that bringing essential necessities to a desperate populace is somehow a bad thing, if its dictator refuses it.