All generalisations are wrong, unless backed by scientifically valid research.
I read fairly much and frequently on my Kindle, on the order of 20 thousand pages this first year. I also read a lot on my phone, and on my laptop, using both the laptop's own screen and an external monitor. I don't find the Kindle's e-ink screen to be significantly better than the other screens for reading. I don't have a problem with my eyes getting tired with any of the screens more than the others.
The e-ink screens seem to be better for some people's reading, and they may be better for most people, but I don't think they're universally better for everyone. The lower contrast of the Kindle screen is certainly not endearing it to me, compared to LCDs, but it's not usually a problem; similarly, LCDs are no good in sufficiently bright sunlight. I pick my reading screen depending on the circumstance and environment.