It's slow, clunky, unstable, it's boring to look at, too bland, too generic, can't sell more than 1 req,takes forever to leave matchmaking, can't leave a lobby if players are found.
You cannot see the player game tags, lvl, spartan look and stance and you cannot tell how the team is set up. No post game medal in the carnage report.
Sometimes the matchmaking cannot find a game so you have to leave which takes a while then start it up again.
If you are in the middle of matchmaking but you have to do something that requires you to leave the matchmaking you need to do it before a lobby is found because you are locked to it which means you're screwed. Other games allow you to leave and allow space for another person who is in matchmaking but halo 5 doesn't.