I don't agree with some of your picks. Yours is quite similar to Steemit.
LBRY is a protocol, not a direct competitor to Steemit. In fact, some people have proposed to use LBRY in Steemit posts. For example, people can upload images to LBRY via Spee.ch instead of the way Steemit is doing it right now, which is upload the file to Amazon S3 servers. With LBRY, while there were computers storing the image -and powered on- it would be possible to show the image. And it is free both for storing and for the bandwidth. Also LBRY as a company aren't focused in video. They provide a client which allow users to upload content. Most of it is in the form of video, but there are also some images. Users upload it, not the company. LBRY can host any type of content, not just videos or audio.
Synereo has a long history behind them They started as a way for put back in user hands the activity in social networks. After many years, they have just released WildSpark -which will finally release out of beta next month-. That new product must be put into the Monetization sector, not the Content Platform sector.
Im not an expert like you apparently... Ive just searched for social networks and this what came up. I dont know that much about it, so thank you for clearing things up.
There is also golos.io for russianspeaking users.
I am not an expert. It is just easy for people to write articles -even journalists do it- just by reading what it is written in the projects home page, without testing it for themselves.
I didn't want you to be taken as a non-expert. I was just adding some information that it wasn't taken into account when talking about social networks and adding LBRY and Synereo as if they were. They are not.