I would add that the D’s and R’s have a tacit agreement between them: we govern 50% of the time and you govern 50% of the time. This is much better, for power seekers, than to open the system up.
In many district elections in the USA, the result is often known before the first vote is cast. One party is going to win, the other party is not. So then the more important contest is between the candidates for the party nomination. But maybe 5% of citizens vote in these internal party elections. Kind of like the feudal days if you ask me: 5% get to make all the decisions.
I will concur that PR is more “democratic” than FPTP. But I think we need to look beyond PR — and get rid of parties altogether. Let’s elect politicians based on their character and capacity. Let’s promote the better politicians higher based on their work in government.