Pokémon truly died when sprites stopped being a thing. Since gen 6 all we've been left with are bland, lifeless 3d models that suffer from washed out colors and a lack of detail and personality. Sure the 3d animations are fun to look at for the first 1.5 minutes but after that nobody over three years old really cares about them. Gen 5 did it the best when sprites had detail, vibrant colors and hit that sweetspot of having just enough animation to evoke a sense of dynamism.

When 3d models came along we knew that given the amount of time and other resources required to create these models, that one day games would only contain a limited selection of Pokémon. Gamefreak cannot just keep putting out ~150 new Pokémon every generation and meet fans' expectations for the quality to remain the same, let alone improve.
If sprites were still around then we would not be having this problem today.