I've tried Readlang briefly and thought the look of the site was much nicer than the clunky interface sported by LingQ, but I still didn't feel ready to make free reading a major part of my study as a ~B1+ self-learner of Spanish. Most texts for natives, even children's books like Harry Potter, are still very slow/difficult to read at my current level.
Import tools are nice, but the content I stumble on is often too hard for me to read efficiently. What I really need is help finding stuff I like that is only ~5% unknown words so I can read more fluidly/enjoyably. I'm not sure how to tackle the problem, but if you can crack the content discovery nut it will make the tool more accessible to lower level language students at the "widest" portion of the language learning funnel.
Another thing I've noticed is that Readlang seems very "quiet". Other platforms like Duolingo and LingQ have active user forums where people can share their experiences and problems. It'd be nice to have a discussion place to swap suggestions, get encouragement, and (most important) see testimonials/success stories.
Anyway, good luck. I hope the product is still around when I'm more advanced and ready to make reading a bigger part of my study.
Good beginner content is a big problem, I agree that recommending a stream of content with ~5% unknown words would be very cool. On the other hand, being a small indie developer, maybe it's better that I concentrate the smaller niche of advanced learners since I'm then not directly competing with Duolingo and other highly funded sites.
I would like Readlang to be more social, but haven't got around to it yet. I thought about adding disqus comments as a quick solution but they aren't ideal, requiring you to log in a second time.
It's probably more sensible for me to polish and optimise the current feature set first before adding social features.