Nonsense. Google bought YouTube when it was a small upcoming videos site company and turned it the giant it is today.
The job of of a ceo is to buy a tech company and improve on it and not just simply buy it and hope its gets better. Otherwise you’re uselsss which is what Phil Spencer is.
YouTube is larger than it was but when Google purchased it it wasn't small. You're talking about literally at the time the fastest growing website on the web with over 100 million video views a day.
YouTube grew pretty much being a monopoly that no other company got serious about taking down until it was too late.
Tech CEOs guide the general direction of the company but the things you blame Phil Spencer for (quality game software) are decisions he's not in the weeds with just like Nadella wasn't.
Look at PlayStation. They've had many people in that role since the original team and it hasn't had much of an impact overall.