Both the Democrats and the Republicans are right wing, therefore “centrism” and “compromise” are necessarily also right wing. Bernie Sanders, in calling for welfare capitalism, is objectively a centrist, so centrism is as “extreme” as is allowed in the leftward direction.

both political extremes go down the authoritarian route

Firstly for all practical purposes there is no left in the US, “extreme” or otherwise, and secondly horseshoe theory is bullshit.