You are neglecting the compounding effect you lost on the tax you paid on the initial Roth investment.
Generally speaking, a Roth IRA makes more sense if you are a lower income earner, or expect to be in a high income bracket in retirement.
You are correct, that’s the basic premise. I never understood how it could be in a higher income bracket in retirement or even if I’m in the same bracket be drawing more income. But according to the calculations, I will be. Hopefully that is.