I've understood it very well, I find it very funny that people which say stuff like Google is a private company and should do what it wants are the same people which say Google should respect net-neutrality (peering agreements, ...) and not do what it wants when it's about core networking and not social media.
A utility is something that is regulated, it comes with a lot of caveats and challenges. It's not just a label you can put on anything, you need to actually define and set boundaries etc to what the utility provider is required to do etc.
This has happened for ISPs, but none of that has happened for Twitter, Facebook etc... thus it's not a utility, thus it's not bound to the free speech amendment.