My opinion on the subject is this:
50 Shades is a romance. It’s not a great literary work but it’s entertaining for what it is and it opened a lot of doors and windows for people to realize that being kinky, submissive, etc is okay. Every generation had its book that did the same, some with greater success than others, but much like “the Story of O” and the “Sleeping Beauty” series, these books provide a look into our world and some things it does well like showing negotiations over a contract and safe words.
As an educator and venue owner I’ve seen many people come into the lifestyle over the last 10 years because of these books. It also gives people a way to break the ice when talking with a potential new date/relationship/partner because most everyone has heard of “50 Shades” so it’s easy to say something like “Hey you’ve heard of 50 Shades, well I’m into that or curious about it.” No it’s not hard core but I don’t believe that takes away from its value as an entry point for those wanting to explore.