However if people vote uncommitted in the primaries because they are convinced Biden is Genocide Joe then they aren’t going to want to vote for Biden in the general election.

If he changes policy, why not? People can make mistakes. Ideally, I'd rather not support someone who has such a past history and I'd be skeptical that the change is a long-term change rather than just trying to appeal to voters in the short-term, but given the other likely outcome, someone it certainly would be a lot better outcome.