Language learning is hard work, and most people fail quickly at it once they realize it'll be several hundred hours before they'll be at a useful level. That's probably why it's so hard to make money with a product primarily tailored to the needs of intermediate and advanced learners. Learner attrition means that most people attracted by the idea of language learning don't make it that far.

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.