The physical/special split and WiFi features were a godsend, but nearly everything else was unremarkable. The gameplay was SO DAMN SLOW, new evolutions to old Pokémon were ugly, the spread of Pokémon across the region was bizarre (almost zero fire types), HM's still terrible, etc. Ruby and Sapphire, while having their own issues, felt fresh and the gameplay was fast. DP just didn't impress enough for being a new gen on new hardware. Maybe Platinum fixed some things but I wasn't willing to bother by that point. Gamefreak often does the whole 2 steps forward 1 step back and this was the perfect example. Luckily gen 5 came and fixed almost all the issues I had.