I think a lot of people are misunderstanding the point of the series. They are telling their own story set in the Halo universe. It's not going to be an exact copy/paste from the games.
The Halo game were great. I've been a fan since Halo C.E. on the original Xbox. You just can't go into the series expecting the same story from the games.
There are certain elements of the game that just don't translate well over to a long running TV series. There are also things in the TV series that probably wouldn't translate well over to the games. That's why they created the Silver Timeline. You have to separate the two and realize each is it's own thing. If you can do that you can enjoy both the games and the series.