You said Fable was highly regarded. There hasn't been a new one in years. Never mind Peter Molyneux was a snake oil salesman. That has nothing to do with a potential new Fable being announced. But if your claim for well regarded franchises is including two that are almost a decade old then you're not doing a good job.
You don't think people would be excited about a new Fable game? What is the time frame for you where a game quits being capable of being highly regarded? By your logic, no one cares about Half-Life anymore, since we're over a decade away from its last (non-spinoff) entry in the series.
Also, Peter Molyneux is no longer at MS. As I understand it, Fable 4 is being developed by the folks who made Forza Horizons, with support from Rare for water physics.
Studios are only as good as the people in them and the willingness of those in control. Microsoft bought Rare and immediately ruined them and cancelled already in production games. It's not a given that buying studios = good exclusives.
Microsoft ruined Rare? Big fan of Playtonic are you? Love Yooka-laylee? And what, you liked Diddy Kong Racing that much? Donkey Kong Racing was the only game that got cancelled during that purchase, for obvious reasons (though MS did let Rare continue to support Nintendo's handhelds).
I'll agree that Grabbed by Ghoulies was lame (Stamper brothers were still involved then), but Kameo and Perfect Dark Zero were solid. I'll agree that Don Mattrick was an idiot, and almost ruined Rare by having them focus on the ill-fated Kinect, but Don Mattrick isn't at MS anymore, and Sea of Thieves is a damn good game that continues to get better. Hell, even Banjo Kazooie Nuts & Bolts was good, but people threw a hissy fit because it wasn't a pure 3D platformer, even though that genre's popularity had waned considerably since the previous generation (and no, don't try to bring up Mario; no game developer on the planet is remotely on Nintendo's level).
In the end, MS's previous issues have all come down to leadership. Peter Moore is an incompetent moron, but he's gone. Don Mattrick is an incompetent moron, but he's gone too. Phil Spencer has been working the front lines at MS for three decades, and he seems to have a solid vision and it's generally understood that he's had a good relationship with the studios in the past, even when leadership was garbage. Xbox Series X is Phil Spencer's baby, so I have every bit of confidence that it will have a fantastic launch.
And as far as I know, Obsidian, Double Fine, and Ninja Theory haven't lost any key personal since MS purchased them. And if anything, Rare is on the uptick these days. I mean, seriously, have you even played old Rare games lately? Let me assure you: They have not aged well.