The repeal the 19th meme is funny but now I'm not sure that is as much of a problem.
The property requirement meant that only those with skin in the game were the ones who got to decide who governed. Without it we have paupers and indolents with the power to spend money that they did not earn or pay.
That inevitably leads to the death spiral from the famous quote:
A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.
Obviously no political movement can form based on this principle since our current "conservatives" are too spineless to even fight for voter ID requirements. But at least it is within the overton window allowing for public discussion.
The most fundamental problem IMO goes right back to the beginning in thinking of voting as a human right. Voting is a means of making decisions, and the useful thing about democracy is combining a lot of little input signals to steer a big ship. Come up with a system that excludes me from voting, and I might be butthurt about it, but I'd much rather live in a society where the people that can vote make the correct decisions than in one where I can vote but so can every idiot, and the worst decisions are made.