An approach that's being tried elsewhere is a vacancy tax. This encourages either private use or leasing of the properties.
Or you could allow more houses to be built. The market can’t work if building is restricted.
Unfortunately there isn't unlimited land with a good location.
So let people build up like every sane city does.
...and then have them taken over by absentee investors.
Manhattan?
Then investors will buy the new apartments/properties and leave them vacant. It happens in cities all over the US and Canada.
I remember reading that Sweden didn't want retirees to be subject to random market forces for housing. So they subsidized housing and in exchange restricted the profit when sold. So, really, the point is that we could set up systems to do whatever we want. Those who say "it can't be done" are expressing a philosophical position - while falsely claiming that they are just stating facts.
Reassess and tax property as the primary means of funding the city. That will almost completely eliminate the problem very quickly.
Unfortunately Prop 13 would make that pretty much impossible to pull off without changes at the state level.
I think enough people are waking up to the idiocy of Prop 13 now that it has a good chance of being repealed. It's being voted on in November 2020.