When talking about things that cost money, it’s always either/or. If you spend $X someone in the top 50%, you have $X less to spend on those in the bottom 50%. And personally I prefer that Democrats generally prioritize spending for the bottom 50%.
Democrats also support things that help everyone and don’t cost the government anything. For example, the ACA banned insurance companies from rejecting people with pre-existing conditions, banned them from raising premiums on sick people, banned them from dropping people in the middle of treatment. Those were all major problems before the ACA, and the ACA helped everyone by fixing them.