Let me first say that I don’t agree with this doom and gloom sentiment at all. In fact, I’m finding the premise of this thread more than a little bit sensationalistic, and the title makes me roll my eyes hard. With that out of the way, let’s get into details.
Yes, Xbox launching without a strong launch title that Halo Infinite was supposed to be will be a significant setback. However, MS have been readying themselves for the possibility for a good while. In one of the interviews earlier this year Spencer was asked about the potential effects of the virus pandemic, and he said that they were talking about that a lot. At the time he was sure that the hardware would be ready in time, but Infinite was up in the air. However, they were so confident in their overall proposition that they were considering launching even without Halo. In the following months Infinite was seemingly back on track, but then the showcase happened, and we all know the rest of the story. The bottom line is, while launching without Halo will be a setback, it’s not something that would put MS in panic mode, because they’ve been toying with the possibility for quite a while.
Others have pointed it out already, but both consoles will be supply constrained at first, and they are both likely to have reasonably strong launches. Even Xbox One had a good launch, and that console had a lot going against it. People already invested in the ecosystem would be keeping things going for a while no matter what, 2021 was always going to be more important, and by then we should have Gears Tactics, Flight Simulator, Halo Infinite, and who knows what else (at the very least I’m expecting a couple of new games from the publishing team).
Also, while GamePass alone might not be a system seller (it’s debatable), it’s far from everything that Xbox has going for it. It will also have the best versions of most multiplatform games, likely the best BC enhancements of current gen games (and by default the best enhancements of older BC titles), timed console exclusives, and a sizeable amount of promising first party games coming down the line. Overall, it should be a platform attractive to many people, even without the big hitters at launch. And of course, the pricing will be crucial for both consoles. That’s why neither company has revealed their price points, that’s why Microsoft has Series S still to be officially confirmed (and it could upset the market balance in a big way, depending on what it is, how it’s priced, and how effectively it’s marketed), and that’s why they’re expanding the Xbox All Access program substantially.
I’d also like to add that I get the impression that OP believes that MS are not sincere when they say that selling their new hardware quickly is of less importance to them than keeping people invested in their ecosystem regardless of what hardware they’re using. MS had every capability - and certainly the resources - to approach things differently had they still believed in the prime importance of the traditional model, yet they’re taking their own approach, one that will not see the overall Xbox business “in real trouble” even if one of its core pillars - Xbox Series X|S - falters at first.
TL;DR - there’s an exciting year and an exciting battle of industry giants ahead of us, but I believe the OP is way off the mark with their concerns.