The pressure campaign for RBG to retire was when democrats still held a senate majority with 53 seats. Republicans blocked Obama's SCOTUS appointment when they held the senate majority. In 2016, republicans simply just didn't allow a vote to happen because the senate leader sets the vote schedule. The nuclear option had already been invoked by that very same dem caucus on all other presidential nominations too.
The scenarios look similar on a surface level but in the details that matter they are leagues apart. If RBG had retired in 2013 or (most of) 2014, her replacement would been confirmed, barring a Kavanaugh-sized scandal. Either republicans would have provided the seven votes needed to secure cloture, or Reid would have invoked the nuclear option to lower the cloture requirement on SCOTUS nominees to a bare majority, like all other positions. Either way the nominee would have been confirmed.
It should be done, but Biden has never had the opportunity.
The size of SCOTUS is set by statute, and would need a law passed by the house and senate to do so. Democrats don't hold the house today, but did in the prior congress. That vote likely could have succeeded. It would have failed in the senate. At the time the senate was 50-50 and I cannot possibly imagine any scenario where Manchin and Sinema would have voted for that law. King and Feinstein wouldn't have been certain votes either, but likely winnable if it came down to the wire. Even if all of them did vote aye, regular legislation can be filibustered and there is definitely 0% chance that Manchin+Sinema would have voted to kill the filibuster.
Dems need a house majority and at least a 52-48 senate majority for this to happen. I suspect that rage has already faded enough that it won't happen even then, barring SCOTUS doing more Dobbs sized awful decisions.