>>35273947Putting it simply, Pokemon grew and the internet developed.
Official Pokemon sources now make their new info more easily attainable for the average fan, so Serebii's become just a redundancy there. Other sites for general Pokemon related info have gained relevancy, too. And when it comes to leaks or Corocoro, I honestly would rather just use /vp/ or Japanese imageboards.
And like others have said, that archaic web design may have that nostalgic charm but it's really not doing the site any favors. As much as people wanna meme about bulbapedo, it's much more aesthetically pleasing and user friendly for getting stuff like a Pokemon's stats, movesets and where to find them in games.
Serebii is still one of the most popular choices for info but it's definitely not the best anymore.