I just discovered this when trying to book a rountrip BNA-ATL flight. Honestly I don't really care about Basic Economy because my AMEX gives me zone 1 boarding and checked bag so the only thing that's missing is seat assignment. You're not even going to be earning mileage on a SkyMiles ticket anyways so I don't see the downside.
I think it's funny that people are so unhappy with basic economy. Clearly its what the people want. Less amenities and cheaper travel. Delta is able to sell plenty of these cheap tickets and raise the price a little bit for those who want seat selection, etc. It's important to remember that for big families, flying is often not an option. Basic economy makes it a little easier.