Democrats (and politicians in general) have to get back to the axiom that says all politics is local. Voters eat this "Hometown Glory" type of stuff up, and its crazy to think that Democrats are going to be able to win in Republican-leaning seats if they try to nationalize the elections.
Recruiting candidates in every race is essential too. Some of you on this forum may not like it, but that means propping-up and supporting moderate-to-conservative Democratic nominees in places like the South and West.
One of the ways some of the Texas House Democrats used to hang on in the '90s and '00s was by pitting urban/suburban and rural residents of a district against each other. In a lot of cases, a rural white Democrat with no VRA protections would be drawn into a district that had been made more Republican by tacking on the outer fringes of Houston/Dallas or a mid-size city like Longview. The Republican candidate would inevitably be from the city because there were no rural Republicans at the time. So the Democrat would basically drive around to all the little podunk towns and say, "Do y'all really want some city boy from Dallas working for you? Do you think he has our interests in mind?"
What I think Democrats (and Republicans sometimes) don't realize a lot of the time districts
are still drawn this way. The only problem nowadays is finding rural Democrats to run.