I'm an avid Pokémon fan, I like almost every game.
However, I don't like BDSP (Brilliant Diamond, Shining Pearl) because I think they failed miserably. They were new, being the first main series Pokémon game to be outsourced to a different lead developer, being ILCA. This was definitely new, but it led to a game that was clunky and wasn't fun. Unlike some people, I have no real issues with the graphics. The game didn't feel new, it didn't add to and improve the original games, it just directly remade them, faults and all. Most of the improvements made by Platinum weren't added. The games just created a remaster of Diamond and Pearl, but without the charm.
The games also have a horrible difficulty curve, the games are reasonably easy, until the Elite Four. The Elite Four is horrible to fight, since they use excellent strategies. The Pokémon are also designed to be just shy of competitively perfect, giving the Elite Four an advantage that you cannot truly counter. It isn't the kind of fight that is difficult, but fun, it's just a miserable experience.
Then you get to Cynthia. Her Pokémon are competitively perfect, creating a battle that is the least fun I've ever had in f*****g Pokémon. That fight took me 20 minutes because I had to heal-stall her.
The thing is, this kind of fight could reasonably exist in a game. As an optional post-game challenge, not as something needed to beat the game. This game failed to consider a significant portion of Pokémon's target market, kids. This game is too difficult for most kids, younger kids don't know complex strategies, most kids (and adults) just want to use their favorites. This game isn't fun to play, and I didn't touch it after I beat it and got Giratina. Until recently, I'm working on catching all the Legendaries in the game so that I can transfer them to different, better, games.
I think ILCA has the ability to make a good game, but this was a very bad first outing.