At the same time, they also entertained increasingly extreme rhetoric within the Democratic Party to maintain their voters, who without at minimum lipservice to their pet causes would likely have considered actually abandoning the party doing all of the things you mentioned.
Whereas you guys were all moderation, peace and harmony, eh?
I'm not actually totally averse to the view that the left has moved, but I think something very different has gone on. Firstly, I think new generations appear, and new generations have fresh ideas, and these leave behind those older. They fought for what was trendy when they were young, and when the new youth bring the next idea, plenty of them are not on board. They got their progress, and they're not interested in the next.
Secondly, I think this is the internet, and its echo chambers, and its tech platforms with outrage-driving alogrithms. I think the whole of society has been polarised and embittered, and the centre is collapsing from both ends.
The right then has a nifty line in concealing its bloodlust and animosity in wholesome-sounding ideas of defence from extremists - which you of course parrot like all the others. And if one day your elites do send in the stormtroopers until the rivers run red with the Democrats' blood, you'll be cheering on every bullet fired, because you have already written your defence of them doing so. This forum is proof enough that you excuse the Republicans everything, you're not going to stop doing so if they turn to mass murder.