I'd say like with most things, simply going through the material is not enough. You need to follow the tips like reading the script out loud. This has had major impact on my ability to learn and furthermore speak the language.

I've been using Duolingo daily for soon 3 years (pro user), approx. 30 min, learning Japanese. Although I also use other apps for deeper knowledge and understanding of the grammar, I would be lying if I said duo didn't work for me. I understand most of what I've learned so far although reading is still a challenge, especially text with more complex kanji in it.

You say you've gone through the course but is that still true? at least today there are 810 quests, each with a meter for you to fill up.

Id be shocked if you got through all that and still didn't know how to count to ten.

Duolingo is no silver bullet. You still need to be really interested in learning, practice as much as possible and last but not least, investigate and deep dive into the grammar.

In case you're interested, here are the other apps I use for learning Japanese. - KanjiGarden, for memorizing kanji - Takoboto, my favorite dictionary - Renshuu, good for deeper explanation of grammar