I have the exact opposite experience with Anki. I use it to memorize vocabulary of a language I'm learning, a language completely different to other languages I know, and my retention before and after I started using Anki is night and day. Frankly, I was floored once I realized how much faster I was learning, and how easily I can recall even words I last practiced or used months ago.

I make and maintain my own cards/notes, which I think is part of why it works so well - it's tailored to my learning, not to someone else's.