The house they would be buying would come with a much higher tax bill.

Personal anecdata: My folks bought their house for ~70k, it is now worth ~1.5M. The taxes are about 600/year for them, they have no mortgage, paid off decades ago. If they were to try to buy their house again, it would be ~8k/mo just in taxes and mortgage. Moving out of the metro isn't an option as no medical services really exist outside of metros in CA anymore. Same for many other services.

Many older homeowners in CA cannot afford to live there anymore, essentially. They are in a gap/trap.

Yes, you could revoke Prop 13 and let things adjust, but even incremental steps would cause wild swings in property values as the market readjusted, likely causing knock on economic effects in the whole US economy.