I tend to agree, but I also think they have some utility for those who might be able to construct a portfolio, but do not have the time or inclination to maintain it, for instance, periodic rebalancing. A robo-advisor like Wealthfront would do a good job of routinely and in a tax-efficient manner maintaining an investment account.
I would say that Wealthfront really offers a very longterm horizon approach to investing. It is one that fits best with taking a chunk of money and giving it over to them for a 15-30 year growth or placing a consistent "pay-yourself-first" strategy where you invest $10+ a week/month for that same long period. Set-it and forget-it and let their algorithms do their work, and be glad you did a decade or so hence.
I'm viewing it as a longer term way to invest and let their formula work while I focus on other things. It's only one prong in a multi-prong strategy I have when it comes to diversifying. Based on the early results I'm seeing, I'm leaning towards investing more periodically, just have to figure out how much and how often.