That's because they are idiots who are pushing arena without giving the base game the fixes first.
Couple that with xbox gamers being notorious whiners and blaming anything and everything for them sucking, and you get this terrible decision. It's not like the game wasn't on ropey ground recently, the dev team gutted because of it. Then they suddenly get streamer attention and even top Fortnite at one point on twitch, nail the timing of a sale and people come back. Then this.
It's feckwittery of the highest level. Just a plain stupid, lazy and cowardly decision. What's worse is the xbox players moaning don't realise that they are just going to continue to get dumpstered anyway. I switched to controller yesterday and had no problems, Summit went one further and did it whilst restricting himself to 30fps and had no problems.
The game needs balancing and fixing for xbox, not this.
I've always told you xbox was cack but you never listened.