It was the end of the DS era, and Gen 4 gave them a-lot of experience figuring out the system. It ran faster than DP and its online infrastructure was significantly more robust (even though a-lot of it no longer exists). The Pokemon sprites are kinda ugly, but making the DS sprites "animated" is still somewhat commendable. Especially the human characters in BW2, which are seemingly even more dynamic and expressive than the Pokemon. Overall they are in familiar territory and arguably at the height of their craft. The presentation of the world feels like the "end" of their efforts with 2D/2.5D games. It was also before smartphones ruined their entire design philosophy, so they were more willing to add a bunch of random misc. sidequests to the single player game instead of expecting you to play something else.
I think these games have developed an absolutely inflated reputation in recent years less because "they're perfect", and more because people simply aren't happy with the current state of things games. But they're also just all around decent. Not a-lot of huge issues.
