Xbox isn't Nintendo or PlayStation. When you lower expectations, the picture gets a lot less grim. For a device that doesn't see big #s in JP/EU, 7m in its 5th year isn't too bad.
But why should we accept this? The original XBOX sold better than GameCube and X360 sold very good outside of US/UK and ended selling more than Wii in USA. You don't sell 80M+ if you're not globally succesful. Xbox should not be considered lower than the other two, because then it's unfair to the other two because it diminishes their efforts and success.
If XB is at the level of Nintendo and Playstation "oh look, Xbox is doing phenomally", If XB is not at the level of those two "oh look, Xbox is doing phenomally", but when Nintendo dropped the ball with WiiU and Sony did the same the first year of the PS3, nobody gave them excuses, even if they existed. They did "bad", period. If your competition is doing close to 20M sold per year and you're not even reaching 10M per year, you're way behind, and you're way behind because your product is not as popular as the others. And if you make the comparison with yourself, XBO in its 5th year is way behind X360 in its 5th year too.
You can say Xbox is doing fine financially at the moment, but if XBO were doing like X360 numbers in sales they would probably doing way better financially than PS4. So, in my opinion, if you're not reaching your potential, you're not doing good, in any case, you are just not doing bad, but is that enough?
In sport terms, if Lebron James was averaging 10 points per game less than normal this year, he still would be doing good numbers for a NBA player, but he would be critized for not reaching his potential. XB is doing All Star numbers, when it should be aspiring to do MVP numbers.
And I'm pretty sure Microsoft right now must be doing everything they can for the next gen to be ready to get back to the position they were with X360....