I don't disagree. There is a strong argument that SCOTUS term limits can be constitutionally imposed with legislation. But I would be the first to point out that not everyone agrees and of course, SCOTUS interprets legislation, which gives them veto power over their own term limits if that specific reform is undertaken legislatively. Either way, it's never even been tried, so who knows.

There is also an interesting proposal that instead of term limits, splitting the current roles of justices and attaching a length of service to specific judicial roles be used. In other words, have a justice sit on the general bench for eighteen years, and then move into an emeritus role where they remain a justice but take up specialized work for the court. They still "hold their Offices during good Behaviour" for as long as they like in this emeritus period, and thus fulfill the sole constitutional requirement, but others take their place on the larger bench. This idea too would require no amendment, but as good an idea as it is it will very likely never happen. (I think the Brennan Center link above covers this plan as well.)

For myself, I'd be happy if Congress just increased the number to thirteen to match the district courts without making any further provision, which would dilute the effect of the current corruption while opening no new loopholes for future McConnells to exploit. My concern is that if the number of justices are tied to anything, that thing -- like district courts -- will then become the football with which to game the court.