Nothing to worry about. 343's best team is making Halo 5, Halo 4 was bug free with a perfectly running multiplayer mode. MCC might have looked bad to those wanting just to play MP but remember a different team worked on MCC and they were focusing on 4 games on 3 different generation consoles and bringing them together as one. If MCC wasn't broken that would have had a score in the low 90s easy, it sits on a 85 based on its multiplayer which is still one of the best rated next gen games out there.
Halo 5 is being made by 343's best and there only focusing on 1 game not 4. I don't think it will sit in the mid 90s in reviews but I would say it will hover around 88 - 92 metacritic.
Bungie made Destiny which was nothing great, Halo 4 and MCC are (judging off reviews) are better games and there both are made by 343. The company brand does not matter, its the devs behind the brand, not the brand itself.
Halo 4 sold 9 million units + so popularatiy isnt a problem, Halo 5 would sell more then 5 million+ you would think.