I noticed the same thing. I want to cancel, but after clicking several times on downgrade to free level, I get a strange message saying that I haven't done something long enough to cancel?
So, the more I use LingQ, the more difficult it will be to cancel? I wish I would have looked into that before paying. I'm not a fan of having to form such a commitment to a product in general. Now it kinda seems like my progress is also digging myself deeper into some sort of hole :/
I just noticed that you can go to Settings -> Languages and delete entire languages. That's a relief :)
Though, if I were to cancel my subscription, I would be less likely to re-subscribe later, since I would have lost my progress.