Wow, you have the patience of a saint. All achievements. Do you have every other achievement in Halo games?
I still think they may have been working on it quietly on the side, it would need a major reworking, not patch after patch and porting to PC, Scorpio. The franchise is so tainted, they need a win big time and expanding to the PC crowd with Halo 6 probably, it wouldn't be the worse thing to put Halo MCC on Windows, might even be their biggest hit behind Minecraft. The franchise needs some more fans more than ever. Fingers crossed. I hope they've gone above and beyond and improved everything, reworked things, Halo CEA that looks like Halo CE, no PC quirks, added more to Halo 2, remastered Halo 3/ODST and matchmaking for Firefight, Reach. 343's worst aspect, playlist management.