A Two-Party System Makes The Primaries Important

Student loan forgiveness demonstrates why participating in primary elections is fantastic.
This wasn't Biden's priority and it didn't come from his base. If it hadn't been for the primary, this wouldn't have happened yesterday.
It was one of Warren's priorities. The bill that made student loan debt unable to be discharged in bankruptcy is what got her into politics in the first place, and mitigating that harm was high on her list.
I voted for Warren. That vote became part of the committed 15% support she got across the primaries, even when it was clear she wasn't going to win. When she dropped out and endorsed Biden, it was in exchange for him taking on some of her priorities: student loan forgiveness was one of them.
This means my vote wasn't wasted: people who had less support in the primaries couldn't negotiate for as much. Support in the primary translated into representation in the Democratic platform. Biden needed Warren's 15% to win in the general, and in exchange we got student loan forgiveness and Janet Yellen in Treasury.
Several things went into how effective that was. For one thing, Biden was confident that Warren could deliver her 15%. She hit the road for him with the same enthusiasm she had campaigned for herself, because it wasn't about her: it was about her priorities, and campaigning for Biden was campaigning for her priorities. We voted for him with almost the same enthusiasm we would have voted for her, because it wasn't just about her, it was about her priorities. And we knew that he knew he would need us again, both this fall and two years from now, so we could trust that he would follow through. And he did.
If you ever get frustrated with the "two-party system", I highly recommend getting involved earlier in the process. In American politics, we form the coalitions first, and then we select which of those two coalitions we would like to be the government. Forming the coalition is messier, but it is also a lot more satisfying than showing up at the end & picking between coalitions someone else designed.

In the primaries, it is strategic to vote our hearts even when our candidate won't win, because that is how we get our priorities adopted as party priorities. And then we go knock on doors when the general comes around to make sure our coalition has the power to get them done.