It is true that the majority of blame for the current political landscape (and the supreme court) falls on the Republicans.
But that doesn't mean that we can't point out the foolishness of "progressives" taking a course of action that may have been a symbolic victory, but leads to real harm in the real world.
Perhaps. However, you can't rule out the scenario is that Moscow Mitch would have just blocked the confirmation (unless she retired in the first couple of years of Obama's term, but that would have drastically shortened her career). End result is that you'd still end up with a republican majority, you just would have had several years with an 8 member supreme court.
Yes, the Democrats have to do a better job at playing 'hardball' (both regarding the supreme court, and with politics in general).
However, keep in mind that the longest serving justice right now is... Right-wing judge Clarence Thomas. He is younger than Breyer, but he's still in his 70s, and if the Democrats manage to hold the White House in 2024, its possible that the Democrats will be able to nominate his successor.