I've thought the same way for a long time, but people always argued that it would leave behind everyone outside of progressive areas.

Which is true, but well what's the alternative? The bureaucratic hurdles of a federal government are too immense for it to be fully responsible to people's needs, even when you don't have a government which is perpetually locked in a stalemate at best.

Grassroots movements by definition need to start at the municipal level; and leaving everything up to the federal government in a top-down approach is what paves the way for centralization, consolidation of power, and the resurgence of fascism.

My red state makes "preemptive laws" to undo anything remotely nice that the more liberal cities try to do (bike lanes, solar panels on school roofs, municipal banks).

There's tons of corruption on the municipal level as well (things like large development companies and Flock bribing politicians to get approval), which is kind of discouraging. But, I think you need to attack the problem on all fronts (federal, local, primaries, mutual aid, protest, civil disobedience).