I find that you can't really learn anything, you can only practice something you already know. You won't learn grammar, it's only useful for sentence translation drills. And those drills are artificial, e.g. one sentence at a time, not using context, which is a big part of Japanese. It also has problems with characters with multiple readings (many). It often introduces a character and drills pronunciation before introducing the meaning.
While I have gotten use out of it for sentence translation practice in addition to other studies, I likely won't renew. I would recommend using another tool, e.g. LingoDeer.
I don't see this new feature as being useful. Instead of using ML to try to explain what I got wrong, how about just paying someone to write some text to explain the sentence?
Their sentences are already a bit odd. Now I am supposed to learn to talk like an AI? That's very cyberpunk. Sigh.