As much as I like ETF investing, I'm not aware of a way to automate it. I think above is a misunderstanding, with everyone agreeing regular automatic investments are available for mutual funds.
ETFs are also easy to transfer in kind to someone else (like a child) while preserving cost basis. Is that even possible with mutual funds?
Yep, mutual funds can be transferred in kind. ETFs are easier to switch brokerage companies with, though.
Just a warning on that front, after being transferred mutual funds are very expensive to sell. Where ETFs are sold by any broker on the stock market, with mutual funds you must go to the issuer.
Vanguard charges $20 to buy, and $20 to sell "non-transaction fee mutual funds":
https://investor.vanguard.com/client-benefits/brokerage-fees-commissionsFidelity charges $50 per purchase, but $0 to sell:
https://www.fidelity.com/trading/commissions-margin-ratesSchwab charges "Up to $74.95 per purchase" for other mutual funds:
https://www.schwab.com/pricingThose fees do not apply when buying Schwab's funds at Schwab, but do when someone at Schwab buys a Vanguard mutual fund. (Although transfers are free... so you could transfer cash to Vanguard, buy mutual funds... then transfer that back to Schwab?)