Wouldn't this allow anyone to claim that any right is protected by the Ninth, and allow the Supremes to pick and choose what our rights are, subject only to their own opinions, independent of any law?
I really fail to see how this is a major problem.
Here's why.
Suppose Texas banned ear piercing. A random Texas citizen appeals.
The Supreme Court rules that the 9th Amendment does not protect, say, the right to pierce your ears.
This doesn't make the plaintiff any worse off, and it still doesn't prohibit the other 49 states from, you know, just
not banning the process in the first place.
[For the record, I think abortion should be left to the states, for reasons that may differ from yours].