The problem is moderate voters, basically. What mobilizes the left-wing of the Democratic base either turns off the moderates or actually drives them to vote Republican. And without the moderates the progressives don't have the numbers to carry anything at the federal level.
The Republicans have this problem much less because their coalition in practice is less ideologically diverse than the Democrats'. You have lunatics who are single-issue anti-abortion voters, lunatics who are single-issue pro-gun voters, etc. These people are never on the fence and will never be driven to vote for the other party as long as the Republicans side with them on their single issue. Plus as we've discussed in the spinoff thread from this thread the minority-rule aspects of the Constitutional system translate into deep structural advantages for the Republicans.
These factors combine to make it virtually impossible to imagine substantive change coming from inside the Constitutional system.
@Birdjaguar and
@AmazonQueen, are the Democratic Senators willing to abolish the filibuster to pack the court? Because that's what we're going to need for voting to make a difference. A filibuster-proof majority is pointless when the Supreme Court can strike down any law (and has a right-wing legal apparatus which includes both civil society groups to bring suits and the far-right judges appointed by Trump to the federal bench for the purpose of creating splits among the appelate and circuit courts that the Supreme Court can then rule on).
Unless and until 51 Democratic Senators commit to abolishing the filibuster for the purpose of packing the court, telling us to vote Democratic if we want to fix this is frankly insulting to our intelligence.
Edit: I should add that by all appearances the actual Democrats are happy to have this issue as a fundraising ask; I've received about a dozen texts in the last 48 hours asking for money