That strategy is only rational if you believe that voting progressive in the primary will create change faster than the status quo will kill us all.
False. The best strategy is still the best strategy even if the outcome is still bad. Voting for a third party has a worse outcome. Not voting has a worse outcome. Despite voting for Dems still being a bad outcome, it is the least bad achievable outcome. Hence, harm reduction.
And forty years of the party continually fucking off further right at the behear of it's Wall St paymasters screams loudly that that belief is a fantasy, and your strategy is delusional.
On the contrary, it screams loudly that protest voting is not only ineffective, it's counterproductive. When they lose progressives, they don't shift left, they shift right to try to get more centrists.
You continue to hand power to the people making things worse faster and pretend your protest achieves something. It does not, the rightward shift of the Democrats screams this.