As far as my personal experiences, I don’t use android because the accessibility features are quite limited relative to iOS. This is why most people who are dependent on voice on phones and tablets (whether they are blind or use switch technology) use iOS.
Independent of that issue, however, I just don’t personally ask Alexa content questions other then “when do the Warriors play next?” Or “what will the weather be tomorrow?” So I don’t see the kind of failures that you mentioned. I don’t doubt that they’re there, it’s just not how I use the device.
Most likely once Google Home is actually available it will turn out that it’s better at some things, Echo is better at other things, Siri in a box is better in a few cases, Cortana may be better in some cases. Choice is good.
