You offered that compelling arguments have been made to not expand the court w/o explaining them. You still haven't.
I have in other threads on the topic, and a quick Google search yields numerous articles that caution why court stacking is a bad idea.
The judiciary is meant to be the neutral arbitrators of Constitutionality. Judicial appointments should be a relatively uninteresting function of government. Instead, both parties perceive the judiciary as their partisan Maginot line to protect their legislative achievements. Who fired the first shot in politicizing the judiciary? Who cares. In my lifetime, there’s been a series of escalations. Democrats attacked the character of Bork, to the extent that the term “borked” exists in the Webster dictionary as a form of political defamation. Democrats also obstructed Bush’s appellate court appointments because Republicans have had better success in building a pipeline of judges to SCOTUS.
In retaliation, the GOP in turn escalated the use of the filibuster to obstruct Obama judicial appointments and took the unprecedented step of blocking a SCOTUS nomination.
In your mind, I am sure it is acceptable for the Democrats to further escalate by packing the court. This short sighted strategy of course assumes that the GOP will never be in a position again to respond in kind.
Mitch and Reid broke the Senate together. I accept that you will never acknowledge this.