The Apple TV is well liked with Apple users, so a pretty big audience. :-)
You were saying Apple TV is a failed device because, if I understand you correctly (I am not sure I do), it's on the 4th generation because they keep having to release new hardware to include new features. By that standard, the Kindle e-readers are doing the same thing. They keep updating them to add new features. Does that mean the old one was a failure? If you are in the Apple walled garden, the past Apple TVs did what was needed to do quite well (and I thought the interface was better than a Roku 3). Was there room for improvement? Sure, but they still were popular enough. Hardly a failure.
Reading the Sweethome article, I am not sure if get the impression that the Fire TV is all that special. It's good, but there are several options that seem equally as good for different users. In this whole category it really comes down to where do you buy your stuff, and get the player that supports it. I buy iTunes stuff, so an Amazon Fire TV is never going to be any good for me, and vice-versa if you are an Amazon buyer.
As far as the Echo, I like the thing. I am just not seeing what the big deal is for most people. And you need to be in Amazon's walled garden to really take advantage of it (music and shopping). I keep reading about people who love the thing, and they aren't doing anything different than I am, it's neat, but limited.