Having a good, dedicated e-reader is a hill that I would die on. I want a big screen, with physical buttons, lightweight, multi-weeklong battery, and an e-ink display. Reading 8 hours on my phone makes my eyes go twitchy. And TBH it's been a pain finding something that supports all that and has a reasonably open ecosystem.
When reading for pleasure, I'm not gonna settle for a "good enough" experience. Otherwise I'm going back to paper books.
Have you used an e-ink reader? The difference is remarkable. My Kobo battery died this morning, so I finished the book I was reading on my iPad, which was fine, but much less pleasant.
Besides, it's not just about the screen. The lack of distractions in a device that serves only one purpose is just as important to me.