That's in the party primaries - where each vote is literally a stamp of approval. That's the whole point of power in a two party system - you have your vetting

That's in the party primaries - where each vote is literally a stamp of approval. That's the whole point of power in a two party system - you have your vetting and approval at the primary level, where Sanders and his supporters changed the DNC platform. Then at the national presidential level, you have voters side with which party represents them and their interests better. If you aren't satisfied by either then go get people with like minded views to participate in the primary process.