Basing any political stance on the support / non-support of a potential presidential candidate is a sign of passivity.

If you don't think Biden should be the candidate to oppose whomever the Republicans nominate, then you have 1+ years to work for an alternative Democratic candidate in the primary (Bernie Sanders or a baked potato or whoever). Refusing to support Biden in 2024 is a capitulation to the monolithic power of the DNC. If you don't like the DNC, you can change that orgainzation as well, but it will take more than a few years.