Thanks guys for the replies.
Actually I have 1000 word review on a bit more than 100 pairs of shoes at this point. I'm working on adding more, but I did not create 1000 reviews in ~8 months. I'm writing them myself so it takes time. And the review quality is good!
Anyway, link quality or content quality does not seem to explain the extremely sudden drop in impressions and clics (from 500 impressions/day to 0 in 2 days). I'm attaching the screenshot so that you can see how sudden this was.
Also I found a lot of webmasters complaining about this phenomenon over the past months, this article explains pretty well what's going on: https://www.seotool.ee/indexed-not-submitted-in-sitemap
I've spent hours looking, I found dozens of threads in Google Community with webmasters complaining about the exact same problem, but I don't seem to find any solution/explanation to this sudden extreme drop. So I'll keep making my website better and wait, hoping that things will get back to normal at some point...
If you have any other idea/hint on what could be triggering the issue... Thanks again!