Really? So McGovern existed in an environment without caucuses and with universal independent inclusion? Pretty sure that's not what history says, besides the fact that I have never claimed my proposal to be fool proof. As stated, 'more likely' != 'will always' in terms of generating better, more competitive nominee outcomes.
I'm not sure what his relative worth is as a nominee to his worth as a president, but I can certainly tell you with confidence that he was a better candidate than Hillary per all the numbers as they stood at the time and had a better chance than her.
I'm pretty sure that in light of his voting record, wholesale refusal to take corporate donations, stances (which have remained consistent), and his more glaring points of contrast with Hillary particularly in relation to things like UHC, money in politics and so on, no one except the most willfully ignorant could possibly confuse him with establishment neoliberal/third way politics, or even more ridiculously, establishment GOP politics. The distinction is pretty readily apparent even to fairly casual observers.
RE: Bernie's accomplishments:
Bernie Sanders' accomplishments - Occasional Planet
As to the movement, Bernie hasn't gone anywhere, so how can you judge its ability to withstand his loss without that even happening? It hasn't 'survived without him' because it's never _been_ without him.
Concerning nationalization, the de facto nationalization of huge swaths of healthcare pretty readily comes to mind.
Being someone with first hand experience in the depths of Bernie's movement and dealing with the people there, I can tell you we understand pretty readily that he isn't the sort of hard socialist which means nationalization of all industry and public ownership of the means of production, and that 'social democrat' is the more accurate descriptor.
Finally, again, losing the nomination doesn't suddenly mean you're bereft of power. It is an impediment to be sure, but political power is expressed, developed and construed in all kinds of forms. Being a senator on the crest and at the lead of a prominent, rising and increasingly influential movement, while simultaneously being the most popular politico in the country and one of the most conspicuous and well known/recognized, is certainly a position of power by any measure. Even his frenemies among the establishment/DNC recognize this however grudgingly, hence their efforts to use this power and popularity to shore up the Dem's political fortunes in the wake of the disaster that was 2016 and prior.