X1 would've lost either way, the PS brand it just too strong. The only places they have a chance to win in is the US & UK.

This guy isn't with Microsoft anymore, is he?

tagging for a read over tomorrow.

The Kinect becoming the fastest selling gaming peripheral of all time, and selling 25 million at the end of the 360s lifetime might have something to do with it

They fixed all the problems he mentions, price, Kinect, marketing (I assume he means TV, TV, TV) and business practices (referring to 24h check-in and trade in scheme I guess) So why is it still losing to the PS4.
PS3 made a worldwide comeback, X1 seems to only be going for a tie in the US.

It's the best console for YOU ( and even for me honestly ) but that's not a fact, is your opinion.

I didn't go  to the web page to read any further, but I wonder if he acknowledged that part of it is that Playstation is simply, still, a globally stronger brand, and that 8th gen Xbox was always going to have a hard time against a somewhat humbled Playstation?

In a straight head to head, with the same opening price, and similar specs, and no shitty DRM from MS, Playstation would win the world while probably narrowly losing USA and UK. People still like to focus on the fact that PS3 has sold just over half what PS2 sold. But the thing is, after a bad start, lots of bad press and difficulty in getting equal quality in 3rd party multiplat games PS3 still managed to end the generation effectively equal to 360 in install base. That doesn't happen if the brand isn't still strong across many markets. Xbox 360 had a strong generation primarily because of 2 markets. PS3 had a decent generation because of many markets. 

If you want to see how PS is strong across many markets just check out the top 5 all time consoles sorted by "rest of world" sales:

That still was less than a third of the 360s userbase, also when every forum member out there was telling you that the motion control fad was in fact, you guessed it, just a fad and was already on its way out then it seems questionable that MS wouldn't be able to find out the same.

Let's be real MS completely had its head up its ass when it thought that people, after using and realizing the actual capabilities of the first Kinect, which was frankly marketed on lies, wanted to go out and buy another one.

Fortunately for them they've seen the light by now and have completely shifted focus away from the Kinect, sucks for the people that bought one with the peripheral at or post launch but hey apparently most people are super happy with their Kinect and you won't get the full Xbox experience if you don't have one, yadda, yadda, yadda. (The shift from the fanbase in that regard is actually pretty funny)

One wonders why they didn't learn from Sony's PS3 mistakes, like Sony did.

Sounds about right. They're salvaging it but it always blows my mind when companies make what appear to be obvious blunders. Like nobody ever learns from history.