It's not pointless, even if they have no chance of winning (they don't) you show your constituents that you're against Trump's supreme court nominee who is going to nothing but harm your constituents. There are plenty of reasons to argue the guy isn't qualified (he bought something like $200,000 worth of baseball tickets on loan/credit card debt right before Trump named him, clearly the sign of good judgement) and there's even the possibility that he'll enable Trump in this whole Russia investigation. There's literally no reason not to fight this and they're probably even more likely to lose their reelections if they vote to confirm this guy. Senators like Manchin and Heitkamp are the reason people think there's no real difference between republicans and democrats, they vote to appease their corporate overlords every chance they get, there's no distinction on abortion rights if you're voting to confirm this guy, and you clearly don't want to make it easier for your blue collar workers to unionize if you're voting to confirm him.
But sure, giving a F you to the women and blue collar workers of your state is a great idea and they're totally just gonna cruise through their reelection by confirming Brett Kavanaugh

. It's just bad strategy and it shows that they're spineless. Do we not remember how the Republicans did everything in their power to stop Garland from becoming a nominee? Why shouldn't the dems at least try even if it's only symbolic? At the very least it puts the pressure on Murkowski/Collins in their reelection bids as they can no longer pretend to care about abortion rights and all the things I just mentioned after they vote to confirm and it can be used as ammo against them.