How win rates lies to you

Imagine a scenario which Champion A is very good against Champion B but very bad against Champion C. Then the overall performance/win rate of Champion A will depend on the popularity of Champion B and C to a certain extent. In a sense, Champion A may be strong against the "meta" in which Champion B is popular.

My personal opinion on the matter is that a champion that is strong against the "meta" is still strong, so looking at win rate is still useful in this scenario. But we should also keep in mind just because Katarina has nearly 54% win rate overall does not mean that she is strong in every single scenario. For example, she seems to be routinely crushed by Malzahar in games, only manage to win around 45% in such matchups.

The point being, we should look at the game organically and consider other factors like team composition and counterpicks when appropriate. I only have a small amount of data to back me up on this, but I believe that lower ranked players will more often pick into bad matchups (such as picking Katarina into Malzahar) than higher ranked players - presumably due to lack of understanding of the game.