You still have four to six proponents of what the change should be. In the US, you have two. Half the population thinks we should close the borders, give tax cuts to the rich, illegalize abortion, ignore unions, etc., and the other half thinks we should open the borders, give tax cuts to the poor, legalize abortion, listen to unions, etc. This doesn't produce very many people who want to close the borders, give tax cuts to the poor, illegalize abortion, and listen to trade unions, for example.
Also, if the weaker parties keep getting replaced, the replacements are likely different, so people have to have their own opinion to figure out which new one to go with.
You have primaries, we don't. When the parties are weak and small, they cannot afford primaries open to public, since their opponents would choose candidates who oppose the party's policies. Therefore the primaries are open only to party members and you can't be a member of more than one party (the parties exclude the possibility in their statutes). Even if you are a party member, the primaries are extremely indirect and opaque: e.g. in the Social Democratic Party (one of the big two) the process is basically as such:
The budget stalemate in the US Congress was caused entirely by blocks of voters and representatives that coalesced around strong sets of opinions that few people would have come up with on their own, and by political party leaders forcing representatives in their parties to toe the party line. Politics isn't the mind killer. Political parties are the mind-killer.
Parties are also notorious for obliterating information in elections, as well as for encouraging voters to vote sans information. If you went to your polling place and saw a list of candidates, none of whom you'd heard of before, you might rightly refrain from voting and polluting the signal with your noise. Knowing party affiliations makes people think they have enough information to vote.
For discussion:
We want the freedom to form groups that promote political concerns. But it would be possible to keep these groups at a greater distance from elected representatives. Candidates for office could be forbidden from endorsing a particular party. The Congress could be forbidden from basing any procedural rules on party affiliation. Political parties could be forbidden from making large donations to election campaigns, or sponsoring advertising. That's not so different from what we do today with religious groups, which are not much different from political parties.
Political parties are currently officially part of Congress' operation, even though they're not in the constitution. There are all sorts of Congressional rules specifying how the parties interact, who gets to choose committee members, who runs the House and Senate floors, etc. A party leader can punish a representative who doesn't toe the line with many incentives and disincentives.
Make that illegal. Make persecuting a representative for party-based reasons have the same legal standing as persecuting a representative for religious reasons.
I will ignore comments saying "you're an intellectual dreamer", for the usual reasons.