This claim is just not true. And gets tiresome. You roughly end up where those courses claim to be in reading and listening - depending on language it can be over B1. (No course finishes B2, some do have B2 content). I ended up being able to watch some (not all) netflix series in foreign langue and I was in early B1 section. I clearly learned.

You also dont have to pay.

I speak 4 foreign languages, at (fully tested through exams like the DALF, DELE, Goethe Institute) levels of C2, C1, C1 and B2. Take an actual test proving your knowledge and get back to me.

I've spent a lot of time with Duolingo learners. They're all pre-A1. You're just lying to yourself to make yourself think your phone addiction isn't "that bad." Take a real language class.