Acorns doesn't seem like a bad option at $1/month. I don't specifically like "automatically managed", because that hides the actual investments. If you never see the price/share you paid... did you buy at a good price? Will you incur tax if you sell?
For about the past 6 months, Vanguard has made all ETFs cost $0/trade. At Vanguard you can buy Schwab ETFs, iShares ETFs, or any others - about 1800 of them, at $0/trade. So that's a point in Vanguard's favor, and so far others (like Fidelity, Schwab) haven't matched it.
One further point about Acorns... if you don't see the investments, how do you know the internal expense ratios? When I buy VOO, I know that ETF consumes 0.04% per year. But I don't see how you'd know that at Acorns.