It's indisputably in the Democrats interest to pack the Court and the argument that it isn't because Republicans will of the same is completely idiotic. The status quo is guaranteed Republican dominance for decades, packing is at worst a risk/reward. It'd be like being forced to pick from one or two bowls of candy where the first has 100% being poisoned and the second only 50% being poisoned and choosing the first to avoid taking a risk.
You want politics that are even more personality-centric, even more unstable? Do this. I know for sure you have good intentions. But all this would do is help make us closer to Russia in terms of governance style. No thanks.
A RW president and right-leaning legislature would have a rubber-stamp in the courts, and we'd have no one to blame but ourselves.
The Court's independence from partisanship ended with Marbury v Madison