@Midnight9746 Ranked and Arenas is the keyword here - honestly, I don't understand the game mode and even less the difference between Ranked and Not ranked mode.
Play a few games, did find that yes matchmaking is just bad, most players push the action even more than in BR... this mode maybe is somewhat playable when you play set team vs set team, otherwise it is total trash without any carry-over effect.
At best I could say that you can practice you 1 vs 3 here but again how useful it is when enemies are either really bad - you can easily win multiple 1v3 during the game or vice versa as per the concept of BR 1v3 is close to 100% not winnable given time to kill and damage output.
To sum up - I dont and never will play Arenas.