When using Kobo's kepub format, you basically get a modern Webkit renderer. (Note that regular epubs trigger the much worse ADE renderer.) It's a pity you have to use their kepub format, but fortunately kepub is just epub with some extra HTML. I've been hoping for years that Kobo will get its act together and enable their good Webkit renderer for plain epubs so we can stop having to make kepubs, but that hasn't happened yet.
Additionally I believe you can install other software like koreader on Kobos, so if you don't like Kobo's own software you have options, unlike Kindle.
Literally set and forget. Install plugin, get kepubs always.
I imagine there's probably some sort of Sales Executive over at Rakuten that thinks keeping an inferior rendering engine present on the device is just enough incentive for the average user to do as much of their shopping as they can within the Kobo ecosystem.
A bit big for an eReader perhaps (10") but supports Epub and PDF, is a fairly open platform with lots of community activity and they are about to add the ability to sync with cloud services which I think will enhance its usability.
Not to mention the ability to take notes with a pen.
Or there are three similar Onyx Boox products.
The Boox has many different models so specifying a price without a model wouldn't make sense, so I assume you were referring to the RM2.
The RM2 is US$400, which is expensive compared to e-readers, but is not $800. And BTW, yes, it is annoying how USD are just assumed, but that is our reality for better or worse (and I'm not an American).
There are a bunch of little things that would improve the epub experience, like improved navigation and bookmarks (never really made use of these on my Kindle though). The biggest missing feature IMO as a Kindle replacement is the lack of builtin lighting.
The Nook has had the colour-temperature changing feature for a few years now. I have two devices with that feature.