This is the argument that comes up especially when it comes to guns. We ask that the AR-15 be banned. Then people respond with "that won't stop all gun deaths." No shit. But it will stop some. If you asked any victim, or loved one of a victim, if they'd like to do anything to reduce the death even by one, they'd say yes. Democrats know one law won't fix all the problems, but you have to pass one to start to fix the issue. If it doesn't work out, you just take the law away. We've done it before.
One reason many people in general don't want to enact certain policies is because they will take more than one law, as well as time. It can be years or decades to see certain things change. Many people are impatient or figure that if it won't affect them, then it's not worth fighting for. Shame!