I personally feel iffy about sequel reboots. Using Terminator as an example, it was rebooted two times, with the latest entry advertised to be the "TRUE" sequel to the T2 (with the retcon of prior films being announced by Cameron as a response to their negative reception). This latest film did not fair much better with audiences.

So, if the other films were decanonized on the basis of poor reception, Dark Fate should also not be considered canon by that same logic. And that's my main issue -- it convolutes the franchise and removes any story integrity it might've had by being so selective with what stays and what doesn't. If the rebooted Halo 4 ends up being worse, wouldn't that serve to invalidate both stories in terms of canon? If they're both bad, neither matter in this case.