BART has already been bailed out by the state, twice. It has already failed, twice. It very much needs to reduce the level service it provides if it wants to be sustainable, or seek other forms of revenues while we wait to see if ridership returns. Many have suggested BART explore the SE Asian model of generating revenues by developing residential housing, which seems fairly straightforward.
If ridership never returns, then we ought not continue throwing good money after bad, and we ought to adjust the level of service to meet the level of revenues. Obviously the main problem here is that it's literally illegal to just build high density corridors directly adjacent to the transit stations... which is what we ultimately need to prioritize.