The problem is people are subscribing to a party and not to an ideology that belongs to themselves personally. The parties will always adjust ideology. They are not stagnant. Political parties are political organizations, and like all political organizations their singular motivation is the conglomeration of power--in this sense, by subscribing the largest electorate possible to attain their ends. What this means is, with any political issue, as soon as the party's platform on the issue becomes unpopular, they will move their platform into a position it becomes popular again.
We as Americans, will work together better if we recognize that and instead of identifying as Republicans or Democrats, identify our own values. I have no problem saying I'm pro-life, pro-gun but also think we need a more robust social welfare system to help people in the trenches and some comprehensive criminal justice reform. These things make me incredibly unpopular on both sides and I don't care, because I have my own values and my own morals and I'm going to advocate those, I'm not going to advocate a party.
But far too often we see people who subscribe to their party and it becomes an "us versus them" mindset. As the party's position changes their position changes as well because its not about values anymore, its about winning and losing and supporting your team.