Where’s this version of Bernie been hiding the last 4 years?
Sanders has literally had a consistent message of beliefs since the 1960s. I don't agree with every tactic he chooses, but I understand why he backed Biden over Trump once he was locked out of the general.
Sanders will talk about addressing those things then tell us we need to support the people enabling those things.
If you can show me some progress you or anyone else has made on getting those things (e.g. universal healthcare) through alternative means, I'd be very interested to see it. Republicans are at this point straight evil. The Democratic Party at a leadership level is a bunch of entrenched wealthy neolibs who would rather see Republicans win than lose ground to actual progressives like Sanders, AOC, etc.
People believing that that makes the 2 parties the same thing, are either so bought into their own defeatist nihilism that they can't recognize anything but instant and total victory as progress, or they're intentionally trying to torpedo change via democratic means (maybe to validate their beliefs that they know the "proper fix" without actually having to actually have those preferred systems tested).
Sanders is inside the party, using his platform and the broad dissatisfaction post-election to push the party leadership. He's literally striking while the iron's hot. If you see that as a negative thing, or if that makes you doubt him, I don't know what to tell you.