Democrats can definitely keep looking at states like AZ, GA, and NC, but that shouldn't be at the expense of states like MI, PA, and WI. Those states are not at all gone for Democrats, as Obama got more votes than Trump in all three (and even Romney got more votes than Trump in WI!) There are definitely voters in these states that Democrats can win back, as well as people who didn't turn out to vote this year who Democrats could win over.
Those states can be won back by having Trump super unpopular.
I do not think MI or especially WI are coming back. PA can be won back rather easily, though.
Obama did better in NC, IN, and FL when he was elected than Trump did in MI, WI, and PA respectively. Did those states ever came back?