A graph of time played vs rating

I think it would be interesting to see roughly how many hours people invest in the game to reach a certain rating.

This could give an insight into the skill ceiling and learning curve of chess.

Of course it excludes things like practice outside of Lichess but I couldn't think of any such unmeasured factors that would grossly skew the results.

that would be a cool feature

With the API you can get the rating I just don't think you can loop through all or a sample of the players.