I see it as more of a simplification of things. An e-reader was just supposed to be a digital book reader with an e-ink screen, good battery life and possibly a backlight. Current e-readers OTOH function more like a phone with a screen that wasn't meant to support such an experience. I'm not interested in browsing the web, playing games, and listening to music on something like this when there's already a perfectly functional phone in my pocket.

Using an ESP32 just shows that we can strip away all the bells and whistles to keep the core experience of reading a book with an energy efficient architecture.