>>21920964DP was undeniably the darkest series, not that I'm saying that's inherently a good thing since I'm sure we all watch Pokemon to have fun, but for me it made it more enjoyable. The villains like J actually felt threatening, it felt like Ash and friends were actually just kids getting caught up in problems the adults were trying to solve, which I liked.
DP in general felt like they were trying to aim for an older audience. They had all those continuity references, they had the darker story, they had more defined character arcs, etc. I'm going to guess that didn't work as well as they thought it would which is why they decided to just reboot the show when BW came along.