McConnell stated publically in 2013 that he, as the minority leader would not allow Obama to appoint any judges, period (Which was wrong). In retaliation, Reid and the Democrats ended the filibuster on all judges, except the Supreme Court (which was also wrong). In 2016 Scalia dies in Feburary. Obama nominates Garland Merrick and Mitch McConnel says that he will not let a vote be held. His excuse was that it was an election year and no party should appoint a Supreme Court Justice during an election year( an argument first made by Biden in 1992 for a June confirmation of a Supreme Court Justice in an election year). He and almost every single Republican at that time gave their word that was the new rule that no Supreme Court vacancy would be filled during an election year and everyone should abide by it. Mcconnell ended the filibuster on Supreme Court nominees in 2017.
Ginsberg dies in September less than two months before an election that most people in Washington knew that Trump was going to lose. McConnell, also knowing that his Senate majority was in danger, said forget what I promised, we are going to jam through Barrett who had zero experience when she was appointed to the Circuit Court and had only been on the Appellate Court for three years.
You can understand why this has become such a mess, but to say either party is totally responsible is simply wrong and ignorant of the facts. There are enough moderate Democrats in the Senate that there will be no Supreme Court-packing. The bi-partisan Commission appointed by Biden simply is to study the Court system as a whole (they are not even directed to make any recommendations). Biden is not in favor of packing the Court and it will not happen. The appointment of the Commission is to appease the more liberal wing of his party (sort of like when you hear about a bill being sent to a "summer study committee", it is usually a place where it quietly dies.) It is a dog whistle for both sides to campaign on.
With all that said, expect Breyer to retire and Biden's nominee to be jammed through because that is the new normal. I don't believe that this Court is quite as Conservative as most think. Kavanaugh was Kennedy's hand-picked successor (which is also wrong but that is what happened). Thus far Kavanaugh has proven to be more of a moderate vote than most expected. It is too early to tell about Barret because she has no track record yet.