Pokémon fans may see Gen 5 as the best generation ever, but Pokémon Company sees it as the worst.
When BW was first released, it got a TON of backlash from fans, which didn't prevented it from being one of the best-selling DS games of all time (15.64 million, only surpassed by DP's 17.87 million), in fact it sold more than HGSS (12.72 million), and it got a 40/40 from Famitsu, sounds good, right?
What if I told you that... BW is the only Gen 5 product that sold well?
B2W2 only sold 8.52 million, which is more than Platinum (7.60 million), but by Pokémon standards, it's essentially a commercial failiure.
Pokémon RéBURST, a manga that was being published around the same time BW was released, was cancelled.
The B2W2 arc of the Pokémon Adventures manga was put on hiatus until the end of Gen 7.
And overall, merchandise didn't sold well either.
In essence, Generation V, as a whole, is a commercial failiure. The only higher-ups who seem to like Gen 5 as much as the fans themselves are Game Freak, and even then one must wonder if the backlash taught the higher-ups that Gen 5 is the problem, that it's and old shame that shouldn't exist. Not helped by how B2W2 fixed the Pokémon variety problem and still underperformed in sales, meaning that listening to the fans didn't paid off at all.