the only viable left leaning political party in the US

I vote for Democrats because shit, why not? But what is the worth of a party that:

• Does not function as a party (single defectors routinely kill major legislation without consequence)
• Is incapable of countering the rising tide of fascism, or unwilling to do so
• Has no plan to address the Supreme Court, which will continue to kill anything legitimately good if left unchecked
• Is too beholden to capital to push even the most tepid climate change legislation (the Green New Deal)
• Constantly attacks its left flank, preferring to chase the votes of suburban reactionaries
• Isn't even reliably pro-labor
• Tailed popular movements on all sorts of civil rights issues
• Still can't be bothered to even de-schedule marijuana, the most slam-dunk popular policy one could imagine + a huge driver of mass incarceration
• Is on basically the same page as Republicans with respect to foreign policy
• Generally offers nothing besides "at least we're not as bad as Republicans, most of the time"

Where is that party going? It's never going to meaningfully address climate change, it offers only crumbs to the working class, and any social change has to be led from the outside.