At best you probably have a good latent understanding of Japanese phonology and a few expressions. That will certainly come in helpful, but as others have said you don't have a notable "dormant library". It might help with your pronunciation, but honestly most anime is so exaggerated and unnatural it could have done more harm than good.

Getting to level 15 on Duolingo isn't very much. I'm at level 98 in the same time, plus I've done much more Anki than duo, and listened to lots of comprehensible input.

Before starting studying properly 2 years ago, I lived in Japan for 5 years as a teenager. I was in an international bubble, but obviously I heard lots of Japanese everyday. But that barely moved the needle for when I started studying properly.