the "walk away from the conversation" framing assumes that conversation is a place where meaningful negotiation happens.
the democratic party has demonstrated repeatedly that left pressure doesn't move them. they take the votes and ignore the demands, then they act as if they were always going to win and never needed you (at least until it's time to cope about a loss, then we're entirely to blame).
doesn't matter if it's for palestine, trans healthcare, minimum wage increase, universal healthcare, more often than not it's the democrats calling the cops on people for speaking up.
i've said before but your vision of 'left unity' reads like attempts to discipline leftists, ie get us to shut up about things that make liberals uncomfortable and precompromise with them.