I don't think anyone is talking about banning lawmakers from investing in broad market indexes and the like. They're talking about banning buying and selling in

I don't think anyone is talking about banning lawmakers from investing in broad market indexes and the like. They're talking about banning buying and selling individual stocks because that opens the door to trading on non-public information they receive as government officials. For the vast majority of people this kind of passive index based investing is actually what will lead to the best returns overall. So I don't think your conclusion that this sort of change would restrict public office to very wealthy people is correct.