It's Masuda and Ohmori.
Just think about it, when Tajiri was on board with RBY and GSC the gameplay still felt fresh and new stuff was added, but when Masuda and Ohmori came on board, they made everything repetitive, stagnant and went on with the same safe and rehashed formula.
When Morimoto came on board he always brought new stuff, when Unno came on board he always brought new stuff, but when Masuda and Ohmori directed the game always were shit, rushed and boring.

If we Morimoto and Unno as heads we wouldn't be at this point