The Democratic Party chose Biden, what was a tactical choice. The DNC uses FPTP for its primary as well (then has a list of 2000 principal party members whose votes are given additional weight. The DNC is a far right coalition party that still is guided by the interests of its monied contributors. But since the 1980s we've only been allowed to choose between them and the Christian Nationalist monsters.

Even after Occasio-Cortez won her primary, the DNC and DCCC changed their policy to prevent young upstarts like her from pushing aside establishment Democrat candidates. (Some of those policy changes were reversed due to pressure, but still the Democratic party is not interested in serving the public.)

How do we get a public-serving government? Dunno. Some say supporting our community mutual-aid organizations will help. (It will, actually) but in more contentious states law enforcement are looking for ways to harass and arrest mutual aid organizations, even for doing benign things like feeding the homeless. Civil war will lose the plot quickly, and will end up (typically) in a string of dictatorships, each overthrown by the next until everyone is related to casualties of war and are just plum tired of fighting, and we might get a democratic election out of it if we can fend off all the foreign influencers trying to pressure their puppets into power.

There are a few active anarcho-communist coalitions out there doing their thing, but they are continuously attacked by plutocrat financed militants and mischief-makers looking to make an example of them much like FBI's assassination campaign on the Black Panthers. We humans may just be too easily tempted by corruption to create a functional public-serving government that doesn't depend on a labor caste. (But do please keep working on it!)