3 didn’t write then into a corner, it just set up a landmark they refuse to acknowledge. they could have an entire universe of stories about units trying to survive the wars humanity has endured without needing some galaxy ending threat. Reach (the planet) was one variation of millions of similar stories humanity has in Halo and the game exploring it was one of the best, just do more of that!
3 didn’t write then into a corner, it just set up a landmark they refuse to acknowledge. they could have an entire universe of stories about units trying to survive the wars humanity has endured without needing some galaxy ending threat. Reach (the planet) was one variation of millions of similar stories humanity has in Halo and the game exploring it was one of the best, just do more of that!
Practically though, Microsoft wanted the Chief (and Cortana I guess) because that’s what sells. So that was kinda the constraint.
They could have sent him on a space boat somewhere more remote though. Basically infinite without Halo 4/5 and a way more intimate plot.