Here's my understanding: if you use Wealthfront direct indexing, you mostly hold stocks, so you pay a minimal amount in ETF fees. This means your expense ratio is pretty close to the Wealthfront fee of 0.25%.

If you put everything in a Vanguard target retirement fund, your expense ratio is something like 0.18%. [1]

So as long as tax loss harvesting adds a tiny fraction of a percent (~0.07%) to your returns, it seems optimal to use Wealthfront, no?

[1] https://personal.vanguard.com/us/funds/snapshot?FundId=0699&...