They bet everything on Halo, and it went horribly. Possibly one or two more games behind the curtains might have been intended for a launch window, but the development was slowed down so much that they have been moved to the very end of 2021 or straight to 2022 (like Forza).
During this generation Microsoft's console exclusive output has been abysmal in comparison to what they could and intended to do. Twice they publicly announced a game and then had to cancel it before release (Phantom Dust and Scalebound), more came out severely downgraded or very unfinished (Master Chief Collection, State of Decay 2, Crackdown 3, Sea of Thieves), and the rest of their AAA was fine but generally considered either mediocre or too iterative (Forza Motorsport 6 & 7, Forza Horizon 3, Halo 5, Gears 4 & 5).
The scary trend for Microsoft is that several of their studios seem to go downhill over time, rather than consolidate and get into the rhythm for producing good games at a steady pace. Rare was butchered by a generation and a half spent producing nothing but Kinect shovelware, and the release of Halo MCC was not the wake-up call 343 needed it to be (and if possible it seems things are even more chaotic internally now). Huge question marks still linger over Ninja Theory (Bleeding Edge was mediocre, and they are taking absolutely forever for apparently no progress at all on Hellblade 2), Double Fine (why the hell does it take 5+ years to develop an AA that borderline looks like it could run on an Xbox 360?), Undead Labs (took them 5 years to publish basically the same game again, but more broken than the first time) and probably more minor ones I've forgotten about.
Microsoft also have a few solid first parties capable of releasing good games at a decent pace (The Coalition, Playground Games, Moon Studios), but they are definitely in the minority among a lot of mediocre, disfunctional or unproductive studios they have ended up collecting over the years.