Term limits would only require 60. Kick them out that way.
Can't technically be "term limits" as most think of it, without Constitutional Amendment requiring a lot more than just that, but 50 that don't mind removing filibuster can pack the court.
But, technically, that same 50 (with the support of the House and Presidency, of course) could, without formally installing "term limits", could force justices after, say, 18* years (*which just by random coincidence gets rid of Thomas, Alito, and Roberts), to go onto a mandatory senior status where they only are randomly selected to participate in cases under rare circumstances, say if there is a recusal. So that they are still technically continuing to "serve" as required per the constitution, without continuing to cause harm.
As simplest change, would only require a one-word change to an already existing law to place them onto senior status at age 65 with 15 years of service. Just change the word
may to
shall on 28 USC 371
: "Any justice or judge of the United States appointed to hold office during good behavior
may retain the office but retire from regular active service after attaining the age and meeting the service requirements"