You don't need those sites. Find professors in your chosen field, click on their personal pages and there should be a list of all their PhD student's personal pages. Follow those and any related academic journals, throw in Stack Overflow/Exchange, Google Scholar, and occasional HN and you'll be far more informed than anybody wading through countless junk posts on reddit or twitter.
For example if you're a user interface designer or wearables programmer, then you'd benefit from the recent papers from these PhD students more than you'd benefit from spending hours trying to find meaningful content on reddit or twitter https://www.hcii.cmu.edu/people/phd-students
Even that's not enough. I spent the last year or so switching over to consuming news through RSS, moving myself and close friends out of Facebook, and downloading textbooks. I've been teaching myself advanced mathematics that I didn't get a strong hold of in graduate school.
I found myself in the middle of a category theory exercise stuck. I wasn't getting anywhere, and couldn't figure something out. Break time, so I opened my RSS reader. Even if my RSS reader has curated content, it's easy to read. An article about urban planning here, optimizing latency there, and before I know it, an hour has passed. I spent none of that time focusing on my problem, and I'm just as stuck as ever.
I think, at least for me, I need to stem this constant flow of information. I need to take time to step aside of it, live without it, then get back.
You may be interested in these slides from a lecture (yet more information to consume) on how to find answers to grad level math like using oeis.org to identify sequences, where to post on stack exchange/mathoverflow to get answers, using the inverse symbolic calculator ect http://www.cs.cmu.edu/~15751/2016-lecture1.pdf
That lecture drastically reduced the time I spend now finding answers which usually I found myself drifting into the attention economy while I stopped working to search for things.
For example if you're a user interface designer or wearables programmer, then you'd benefit from the recent papers from these PhD students more than you'd benefit from spending hours trying to find meaningful content on reddit or twitter https://www.hcii.cmu.edu/people/phd-students