There are differences, but your questions are valid nonetheless. The two parties are a Venn Diagram:

We can vote on LGBTQ protections, DEI initiatives, abortion, separation of church & state, etc. because the two parties genuinely disagree on these issues.

We can never vote on wars in the middle east, the ever-increasing Pentagon budget, the ever-increasing ICE budget, growing presidential powers, Congressional insider trading, protections for whistle blowers, lifting sanctions on Cuba, closing Guantanamo Bay, the surveillance state, drone strikes, corporate bail outs, the growing wealth gap, etc. Where both parties agree there is no democracy.