Property tax increases are hamstrung by Prop 13 and until that’s repealed, will continue to be.
And while the wealthy always threaten to leave when faced with higher taxes, the fact is that they never seem to actually do so.
The site is based around georgism whose fundamental premise is that taxing land is the universal solution (much like for republicans cutting taxes is their solution to everything: economy going great? We should cut taxes. Economy going poorly? Cut taxes. Deficit too high? Cut taxes.) I don’t put much stock in analysis by single-solution thinkers.