It wouldn’t always be the worst thing in the world if Democrats in the Senate acted like Republicans in the House of Representatives. Republicans know their attempts to repeal the Affordable Care Act won’t succeed, but that doesn’t mean there isn’t some benefit to trying. It keeps their issues in the news and lets them campaign on trying to do something that their constituents want (even though polls routinely show that most Americans, including even some Republicans, don’t want the ACA repealed.)
The reason that opposition to the ACA has remained high while support for new gun regulations has fallen is because Republicans know how to keep their issues alive, and Democrats don’t.
With the Senate up for grabs, Democrats should dedicate the Senate’s agenda to debating and voting on a minimum wage hike, new gun regulations, a new tax package of cuts for the middle class and increases on the rich, and new education spending even if it’s not paid for. Every single one of those policies has majority public support and is opposed by the Republican Party.