The last real Democratic Party primary was in 2020.
The last fair primary was the one before Jimmy Carter...
08 Obama won an unfair primary, but just because he managed to pull it off doesn't retroactively make it fair.
2020 Biden was doing poorly until SC, got his only good performance, and then like a day before super Tuesday everyone except Biden and Bernie dropped, they all started campaigning for Biden. And then the DNC said that was a mandate for Biden and started pushing Bernie to also bow out.
It might not have been an outright fix, but it was more than a finger on the scale and sure as shit wasn't fair.
I have high hopes the next one will show everyone what a legitimately unbiased primary looks like.