Yes, I understand that there are material policy differences. But in the end I don't believe Sanders would get his big stuff done even if he wins.
No, I strongly disagree with this. There are massive differences between Hillary or Biden (or anyone D candidate really) and Trump. They are much better on the environment, our foreign policy is a disaster under Trump, his response to natural disasters is disgraceful, he's politicizing courts and DOJ, on and on and on. He'd torpedo the country in the long term if it helped him win another election. I'm not being dramatic when I say our democracy is at stake (he is open about accepting foreign influence in 2020 if available).
I think you are really underestimating the damage Trump is doing and overstating what you think Bernie/Warren could accomplish.
The Republican party, which was bad my entire life, is getting much worse. Maybe 30 years from know they'll be destroyed and we can look back and say Trump at least gave us that but it's also possible his fucking son runs in 2024 (and could win) and the party becomes more and more Trumpy. So they're the party of shitty economics, no ideas, focus on redistribution of wealth but with all the racism and stupidity of Trump.
It seems like you're not considering that the wrecking ball strategy can make things much worse. I really wouldn't assume that destroying our political systems makes things better. And btw, populism sucks in all forms not just on the right.