Team Arena has WAY to much wonky Slayer MM

Can you explain these Matchups?

https://www.halowaypoint.com/en-us/games/halo-5-guardians/xbox-one/mode/arena/matches/2d81155e-0288-4761-b50e-e522b5c35b25/players/lovelyjoey21605?gameHistoryMatchIndex=1&gameHistoryGameModeFilter=All

I haven’t touched the damn game in a LONG time, now I’ve been back playing for a little while due to Corona. Matchups like these happen WAY to often, and are reminding me why I stopped playing this game. Fix your -Yoinking!- matchmaking!

343 uses the mmr system meaning that if you played a good game even if you are not a good player your status grows and because of that you find better players this mmr system is very flawed and they even put it in the social mode which makes the game very harder I went to play social and all my opponents were champions while my team was at most gold

that is, if you plan to play in ranked mode you shouldn’t play social mode to not increase your mmr