> I think the thing I dislike about Duolingo is it sort of catches the casual person into a trap by misleading them into thinking that by using this app they'll learn another language

But does it? I have learned other languages using it casually (one lesson a day on average.) Enough to read text in those languages and understand basic conversations. It is not getting you to B1, but it is getting you well in to the A's. If you do any type of additional study on the side, you can easily get to B1.

The main issue with Duo is the quality of the courses. It varies a lot. Some of the user maintained ones are fairly poor. Especially for the more niche languages.