Consider how long it took PCs to reach the same stage (with a fraction of the adoption). It was like 20 years from Kenbak-1 to the 90s PC era.
1. Dialing in the dumb phone. No dumb phones support CardDav syncing.
2. Very few dumb phones can function as wifi hotspots for the e-ink device.
3. Few dumb phones can record calls.
4. I forget what eight was for... seriously I had one or two other issues but I don't remember what they were.