There's no telling who would've won a competitive primary, but the process would've allowed the eventual winner to distance themselves from Biden on the right things, have a program that would've actually appealed to voters, and picked their own team to run the campaign, and there would be buy-in from the Democratic base, instead of feeling like Harris was imposed on them.

I don't think she's a bad candidate, but she made the mistake of listening to the wrong people that told her to run to the right and cosy up to millionaires, instead of building on the work Biden had done with unions and anti-trust, which was reasonably good for a neoliberal Democrat.