The Senate represents property, not people.
"What can Democrats do?"
Everyone who has the chance and the wherewithal should be buying property and moving to the districts that need them. COVID has set the future on an increasing path of remote work over the internet.
For generations, 'liberal' schools and institutions have taken the best and brightest away from rural districts whenever possible because there was no money or jobs to stay on the farms. That left the rest at the mercy of the real estate pickle vendors and car dealer politicians running school boards and town zoning. When liberals move in, it's always a bedroom community gated off from the local culture, creating IKEAclaves of affluence.
Democrats who already live in rural areas should get involved with diversification of property ownership and urban-to-rural farming programs.
Republicans own the farms and houses because Democrats don't.
Instead of buying million-dollar apartments in cities, they should be buying gardens and modest places to build real useful communities that show Republicans that mindless competition for the bottom of the wage barrel and blind faith in imaginary beings aren't the only way to be "Amurkin".