Primaries are lot more than just voting for the top of the ticket. There are hundreds of downballot candidates involved. More important, it’s when voters decide what issues need to be addressed.
Nobody named “women’s rights” ran for office this year. But women’s rights activists succeeded in persuading Democrats that it is the most important issue this year.
This is what Democratic activism is really about, you are basically competing against other activists for the attention of your own party.
Finally, if you vote for Democrats in November then nobody should consider you a traitor.