To Garland from Scalia mattered more than to Gorsuch from Scalia. What matters is changing the swing. Replacing Scalia with Scalia maintains but does not change anything.
When there was potential to change that it mattered more. Given there is no way to change that it matters less.
Kennedy, Breyer and RBG and preserving the balance should now be the objective given the relative power that the Democrats hold.
First, I don't agree that it is necessarily impossible to prevent Gorsuch from being seated.
Second, there is no reason you should expect a replacement of Kennedy/Breyer/RBG to have lower incentives for the GOP than Gorsuch, so if it is impossible to prevent Gorsuch from being seated as you claim, it is also impossible to prevent any of them from being replaced with a justice identical to Gorsuch. In that situation you may as well force Republicans to nuke the filibuster just to clearly establish that it is gone so that Dems can operate without the filibuster in the future.