You truncated what he said. He qualified it with "that you could sell on the auction house", which is exceptionally important.
Grinding bosses for drops to build the character that you want offers great direct feedback - you kill the boss 84 times, and he finally drops the thing you've been looking for. The reward is tangible and exciting. Compare to the AH structure, where it's basically "well, I'll grind for things that might sell, and then hope they sell well enough that I can save up for that thing I need which I know will never actually drop for me". The direct feedback and chance for excitement is practically gone, because the things that you are actually excited for come from the auction house rather than the gameplay.
Except that at least Diablo 1+2 were for everyone. I remember playing those for the story and the gameplay. The loot and levelling were a means to an end for me - finishing the game.
The whole repeating the game again on harder difficulties, requiring better loot and grinding was very much an added bonus.
Diablo 3 decided to throw those who were there for the gameplay and story out the window, and was purely targeted at the grind. I finished the game in 2 days and still had half my characters skills left to unlock. What kind of RPG is that?
The Action RPG genre used to be about more than JUST loot grinding. It used to be about so much more, that welcomed players who were looking for all sorts from the game. Some people liked fast twitchy action mechanics, some liked the RPG story elements, some liked endlessly tweaking character builds and some liked loot grinding. But Diablo 3 is almost entirely focused on the last, with little room for the rest.
which is not different from what people were doing on Diablo II for ages.