Putting money in the tax-sheltered (401k, Traditional IRA) helps shelter _Current Income_.
Having a lot in taxable investments is NOT that big of a tax hit when FIRED.
As long as your FIRE expenses (and therefore income) is not big then long term capital gains and dividends are taxed at 0%
(taxable income <39375 single, 78750 married filing jointly).
Taxable income is gross minus deduction
Standard MFJ is 24,000 so total income could be ~100K and still pay no taxes.
So far I'm on a path for 0 federal taxes this year, at less than the above limits.