Fans buy what is available if it meets certain quality criteria. That is conflict in a lot of customer situations and ofc companies want to move burden from their shoulders to customers like "well people buy this product so we don't care making product any more environmental friendly".

Blaming fans on Pokemon games downhill is not completely well. During the time of BW several other factors could have had impact on the sales - some fans moved to different things, maybe economic situation for many was worse, the pokemon anime didn't really do it's job that well (as a marketing method I mean) and If I remember correct it wasn't THAT long after the 3DS was announced.

Also, I dare say that long time fans stayed during BW and it was more of casual players who skipped this gen as Charizard, Pikachu and Eevee were not starters in the game. As far as I know in Japan the game was quite well received - the amount of fan art was absurd. Never before had I seen so much Pokemon fan art spawn in a short time.

BW was a stepping stone for Game Freak. They saw that the casual audience didn't necessarily care about these improvements so what they did was to cut corners, even though tbh they already cut some smaller corners in BW as in obtaining Legendary Pokemon just through wi-fi and perhaps Battle Subway ( I though it was fun but let's be real - it wasn't as diverse as battle frontier).

In the end the company makes the decisions of what kind of product they put on market. Not the fans.