Its easy to complain but the reality of what your demanding is that many more elderly citizens should be unable to afford their homes and be forced out of them. That's not a preventable side effect, that's the desired outcome. It seems obvious to me why many don't think that's ideal.
If opponents of prop 13 want it repealed they're going to have to buy out existing homeowners to get the votes. I won't pretend to know what that would take but you won't get the moral high ground with a straight repeal so you might as think of some sugar coating.
Proposition 13 was advertised to protect the poor and elderly citizens, but its design does not target them. In particular, it benefits those who don’t need help: commercial landlords, rental landlords, and (after Proposition 58/193) feudal estates. And it harms those poor and elderly who are unable to purchase a house. In short, it is an entitlement that benefits homeowners, at the expense of renters and home-seekers. It takes some tautological reasoning to defend its poor design if the goal is protecting lower income households; see the Stevens dissent to Nordlinger v Hahn https://www.law.cornell.edu/supct/html/90-1912.ZD.html
If opponents of prop 13 want it repealed they're going to have to buy out existing homeowners to get the votes. I won't pretend to know what that would take but you won't get the moral high ground with a straight repeal so you might as think of some sugar coating.