The main problems eink solves for me are eye strain and battery life. These might not be issues for you, but I often read 8+ hours in a day.

My experience is from gliders, which are only operated in VFR conditions (not more than 30 minutes before sunrise and not more than 30 minutes after sundown). VFR is nothing glider-specific though, so I can see them being useful in other VFR-operated aircraft too.

In my experience e-ink displays reduce eye strain and attract less attention. This results in more attention being drawn to the outside world, which in turn is a good thing for safety.

I am not at all in agreement with your statement. In some contexts price is not a big issue and the qualities that e-ink brings are worth the money.

Suggesting that e-ink can be useful for "low refresh rate displays in VFR aircraft" sure sounds like a solution searching for a problem.