Most Democrats don't want Biden to run for re-election. Not necessarily b/c he's been a bad POTUS (he's been pretty good all things considered), but b/c many of us feel the time to move on to younger, more progressive politicians/policies is now.
However, if we don't have a viable replacement, someone like an Obama who can unite the party, then most of us will have no qualms voting for him again if the alternative is Trump or someone like DeSantis.
We are just hopeful that there is another Democratic candidate that will emerge by 2024 that can absolutely take whatever the GOP trots out there behind the woodshed