If you're setting your preferred language in English on the website, all further on interaction should be in English. (BTW they have multiple language dropdowns that I didn't even highlight because I'm sure old generations do not know how to use those). Lack of English translated terms isn't something I've personally encountered, and for the reviews it's true I scroll a bit further down the page to see the English reviews from .com

I've used .de very often in the past, and when I stopped using Amazon, as said in reply to someone else https://news.ycombinator.com/item?id=31445473 , quality dropped (among other downsides) when they allowed third party sellers and those flood the product listing pages.

With those specific suppliers (and anything that isn't fulfilled by Amazon), I expect to be possible to have the issues you're referring to. But I wouldn't clump that together with Amazon not being available in some EU countries.