During the accumulation (working) phase, you pay taxes based on your earnings, which is somewhat arbitrary based on your career and whatever else you are capable of monetizing.

During the drawdown (retirement) phase, you pay taxes based on your spending. You would not draw on your IRA more than you need.

Even if I took the 10% hit on purpose, my average tax rate would still be lower than the marginal tax I was saving when I made the contributions. But as others will mention, there are ways to avoid penalties.

It is true that if your marginal tax rate is 15% or 10%, it might not be as valuable. However, as you grow a taxable investment account, the tax generated by dividends and interest (and capital gains, if you sell) will drag your returns during your working career. Ideally, you would probably move into the 25% bracket at some point and those will start being taxed. After you retire, the tax rate for qualified dividends and capital gains are excellent (if tax law remains as it is now) but you will definitely be starting from a smaller base, no matter how you work out the math. If you use that to calculate a FIRE date, you can turn this into an estimate of how much the date changes.

Since it is also impossible to estimate changes in the tax law, I like to have a balanced amount of assets, but I also have the luxury of being able to fund everything well.

While having only IRA assets is a doable proposition, Roth IRAs are not as useful in early retirement. The general "rule" is to use the Roth IRA for low tax brackets, but you might not be able to functionally retire on 72(t) distributions from a Roth, if that is your only option. The 72(t) approach tends to be low for very early retirement (30s) and is varies significantly depending on the interest rates when you start to elect to take it. I don't think taking Roth penalties ever makes sense since now you are effectively taxing the money twice.