If my income is too high for a Roth IRA, is a nondeductible Traditional IRA worth it on its own?

On its own, usually not much, which is why it's typically just the first step of a backdoor Roth. A nondeductible Traditional IRA gives no upfront deduction and the earnings grow tax-deferred but come out as ordinary income later, worse than the capital-gains treatment you'd get in a taxable brokerage account. You also have to track your basis on Form 8606 forever. The value appears when you immediately convert it to a Roth, converting a mediocre account into a tax-free one. So if you can do a clean backdoor Roth without pro-rata problems, do it. If pro-rata rules block you, a taxable account often beats a standalone nondeductible IRA. Confirm the mechanics at irs.gov.