The challenge here is riding the bus is inferior in convenience and comfort, fundamentally, vs other options. Unless price (likely by eliminating any subsidies for other methods; today even a $0 bus fare would still not be enough) or other features (bypassing traffic) make up for it, why would a rational person take the bus? There are probably places on the margin where buses are more acceptable right now (in a downtown core area where they replace a long walk, where other methods are inconvenient), but if the goal is wide usage, this has to be addressed.

Private bus networks with access limited to certain people (employees of companies or groups of companies, universities, etc) seem to work ok; what generally doesn’t seem to work are public buses.

Is the problem density (I doubt Google employees across Bay Area are denser than bus riding public overall within SF) — probably not.

A lot of the unpleasantness is other riders. Without the ability to ban certain riders (either via a whitelist or blacklist), bus ridership will remain limited. BART is bad enough, but whenever I’ve taken muni or peninsula bus service (very rarely)it made the case for this.

Transit agencies are also highly political — unionized labor, political appointees running it, expensive contracts for everything, inflexible policies — so I doubt they could provide the same service as private bus companies.

The solution is probably not public transit, but possibly is multi passenger vehicles. Something like Lyft Line with more passengers, dynamic routing, etc, plus some core routes with scheduled higher capacity service.