Could you point me to some non-academic group organizing to take power in the US? Any channel where its possible to follow their activity or at least their analyses

No one thinks the system is working. The losers say it's rigged, the winners beleive they're lucky they won in a broken system, and the winners eventually become losers anyway. So yeah, the left wants better candidates but the shit part about being on the left, on any progressive front, is that we can't all agree on what's most important so we get stuck with limp, neutrally progressive candidates as an average of our interests. The right, the don't-change or even regressive side, has it so much easier. Just vote for a crybaby that stomps his foot saying "no" to his greens. Even if they debate between Trump or Christie or Haley, whoever, they'll still have an easier time just undoing whatever that black guy or the junkie's dad did.

So yeah, we keep voting at the final game for the wet towel because we saw how easy it was for the other side to start ripping into democracy. We saw what happens when progressives boycott the vote because their favorite candidate didn't win the primary. We saw what happens when half the country argues about turning left, right, staying straight, or maybe even going up while the conservatives only debate about hitting the brakes or throwing it in reverse. We don't have ranked choice or any other better system than FPTP so here we are

Edit:rugged>rigged