What would that have solved exactly? Those seats wouldn’t have been won by anyone further left anyway. The problem is that North Dakota and California get the same number of Senators, despite the former having literally 50x more people.
Which is why keeping the filibuster has generally been in the best interest of the left, even if it’s not ideal right now. I think the Democrats are absolutely fooling themselves if they think the R’s will respect the filibuster if it’s in their way at this point though.