How does a voting block ever get what they want if they simply continue to fall in line and do what they're told? At some point the powers that be know we don't have to address them because they'll vote for us anyway.
Can you think of a group that's like that right now?
No, in fact, I can't think of a group like that. And if you're hinting at AA's, should I pull up the long list of things the previous administration did that was posted earlier?
Being an adult means making concessions and sacrificing. Getting 80% of what you want is much better than getting 0%.
So if you don't actually value liberal principles, and you're okay with an utter buffoon representing the highest office, then by all means stay home in November 2020.
But for the rest of us adults, who realize the world doesn't revolve around just us, we'll continue trying to get the best candidate selected in the primary and then elected in the general. If a non-optimal person is selected, so be it. But they must have larger character flaws than having chose the wrong profession for me to be complicit in Trump's reelection.