Leaving aside the issue of whether or not he legitimately lost those primaries (which is certainly debatable at least in 2016), I think he would have not been a very effective president because both parties in congress and the judiciary would have done everything in their power to oppose any social welfare policies he might have tried to get implemented.
Obviously, he would have been better than Trump, but I do not think he would have achieved much. In fact, I think he would have achieved less than Carter.
I agree with your point to everyone working against him. Btw I love Bernie and voted for him both times. But I'm just tired of leftists shooting themselves (and all of the rest of us) in the foot by spreading anti-Democrat propaganda during and between every election and being all shocked Pikachu when literal billionaires take over the government as a result.
It's usually privileged white leftists who think their political puritanism is justified.
The DNC fucked over Sanders. All of the super delegates were on Hillary's side before the DNC even had its first primary making it seem like Bernie was not a real choice, while the media downplayed him constantly (the billionaire owned media? shocked pikachu face). This was such clear bullshit that the DNC even changed their rules in 2018 to make it so the super delegates cant vote on the first primary ballet, but I believe its because it doesnt make a lick of difference either way. The people who run the country would never allow us to move in a direction of fixing the problems of unregulated capitalism.
The Democratic Party primary doesn't choose the President, though. The electoral college does. At least one analysis of the polls concluded that Sanders could have won the EC.