They did not implement the winning solution as is, but a lot of good stuff came from the winning teams, including techniques (such as SVD) that are in use as of today (or maybe a few years back).
> just a nonsense engine
No, it is safe to assume the recommendation engine of Netflix is close to the state-of-the-art. A lot of money and talent went into it.
Shortly after that contest finished Netflix removed the five star rating system, and dramatically subdued the recommendation engine. Now the vast majority of the content surfacing is universal beyond some small category filtering (e.g. You like crime dramas and horrors so here's a bunch of the most popular stuff from those categories).
Now they have a "match" rating that I have not met a single person who finds useful (it is almost at the point of farce and seems more like a randomization engine).
A lot of money and talent went into something that Netflix clearly decided just wasn't important or useful enough for them. Now they just push Don't F*ck With Cats on everyone.
How is that different from "LeetCode PhD" doing "DP Hard" for 6 months to get into FAANG?
Now it really illustrated to me how data science is still an incipient field. Even the basic Titanic example has a lot of fake solution and a bit of "cheating" (overfitting).
And don't get me started on the multitude of tutorials and examples that only show the loss decreasing graph but the actual results are not evaluated (and thus might have some glaring defects).