I worry about the robo-‘advice’ being tainted with advice that more favorably benefits the advisor (ie: Wealthfront or Wells Fargo) than the one being advised… see ‘Frontrunning’. The one that controls the info, decisions, also controls the market.

There may also be the problem of more ‘black swans’, and periods of extreme volatility. The current more diverse set of people making investment decisions tends to dampen volatility better than a whole group doing the same thing on the advice of a very few people.