Primaries are the right time to criticize incumbents. General is when we all fall in line. Not criticizing politicians when they do something wrong is what the republicans do - we shouldn't seek to emulate them.
Just a reminder that the DNC due to disagreeing on whether New Hampshire should be first primary or not has literally determined that regardless of the outcome that all delegates from New Hampshire would go to Biden this year.
He won a write-in campaign, but that's really not the point.