If you can't see that the Democrats (presumably unintentionally) enabled this situation by proceeding to do little to nothing after getting Trump out, and just assuming that it had been bad enough previously that people will still go for them, I don't know what to tell you.

They are holding their electorate hostage, why are people surprised that people disengage after continuously seeing everything get worse around them regardless of how they vote?

This isn't necessarily to say that I agree with that inaction; nor did I say otherwise; but if we keep on ignoring why things happen and so never addressing the causes, the same things will keep happening.

I always have the same line here, although often paraphrased: I won't discourage voting but in isolation it is not enough, and pretending that it is is deeply irresponsible. Granting authority over your lives to a ruling class (as in, people whose lived experiences become further from yours every day that they hold power, with predictable consequences) is not freedom, it is just choosing the padding for your chains. Voting under these conditions is a surrender of your power to someone 'above' you, not an expression of your power but an expression of the power of the people being voted for, so of course work to prevent ceding it to the worst options (pretty clear who in this case, thankfully) but if you don't take that power back afterwards this general decline and the resulting rightward drift will continue.