Netflix saturating the landscape with poorly executed adaptations of Microsoft owned media properties is almost certainly not worth the short term dollars for long-term erosion of their perceived value, especially without some certainty of securing complementary title launches. Given the shuttering of studios to right-size for the cambrian explosion of slop for COVID era hardware, Xbox probably wouldn't be able to make that capital work for them any better than sitting on licences until they accrue nostalgia.
Halo could be (peak) Game of Thrones level in the right hands, which means the right execs, producers and investors just as much as it does creatives.
Unfortunately, the right hands potentially no longer exist. The current generation seems largely unable to produce good things, with few exceptions (notably Andor)