I'm glad you discovered Sci-Fi shorts, there's a sister pub Fantasy Shorts too. Jim, the editor, works hard to give them a unique feel and look so it's good to see them getting some well deserved attention.
This is a great article. I love reading novels, I hope one day to finish writing one so I hope long form isn't on the way out just yet! While I'd love longer form to do well on Medium, I'm learning loads by having to keep it concise and within a 3-5 minute read. I can see my writing improve massively (I like to think) in just a couple of months of writing flash fic so I'm grateful that putting work on here has forced me to improve :)