It is somewhat simple, but yet complicated at the same time.
Now it is very simple on to way some people say why halo to evolve and why it should not. Most of it can be explain by preference. Like with steak. You will not make all of your businesses by only allowing one way to cook steak. Some people like rare, some like medium well, others like it in a charcoal chunk of rock. With most people, they do not know what type of steak they want until they try it. You grew up always likely charcoal chunk when in reality, you love medium well.
This can be applied to halo and all other games. Most gamers really do not know what they would love until it comes out.
Just like Nintendo made a Virtual Boy back in the 90s (someone fact check me on year) and no body liked it, while the Oculase rift came out a few years ago and everyone loves it.
A lot of you grew up on what halo was. No sprint, very little ADS, Weapon control that you have to memorize both where the weapons spawn, and how long it takes them to spawn back into play. When that was removed from halo 4, a lot of the old people hated it. They thought it was an awful thing and was taking away from the halo games. So what does 343i do? they take it out of Halo 5 and put it back in.
Now what about the people that like medium well and the Rare steaks?
Well we start by adding items to it that people might like, and somewhat that will make other people come from different games and different generations to play Halo 5. 343i will add somewhat COD controls so people from there can transition easier over to Halo, 343i added in different movement options to allow faster Pace so it feels like actions happens quicker. Add in different levels so It is like the traditional halos.
This also comes into play with how big companies and Youtubers say about games and steaks as well. When a Popular Youtube says positives about a game and recommend in to people, people want to be “hip” and “in the now” so they run and get the game ASAP, boosting the talk and sales of games. However the problem can be the other way around. If something negative is said about a game by someone popular, then the other effect will happen, but some people say “Bad publicity is still good publicity”
This is 343i way of getting as many people into the restaurant to have their wonderful steak as they can. Get Big YouTubes and people to test out there game, write a review and just talk about it, I mean besides them making finishing touches to halo 5, Why else have the beta be a year ahead? Word of mouth and interwebs.