Please understand that arena rankings is not directly proportional to your power level that is why you will still see fully ascended max level teams in lower ranks
There can be several reasons for this.
One is the player is a whale which bought evertlything that he needs, summon, chickens, max ascension and artifacts.
Two, can be a player who already maxed his hall so no reason to grind arena at all.
Three, lazy high level player who still play from time to time but not able to maintain arena ranks.
Four, just inactive players.
Now, they have made a change in arena matching (not sure what they did, or if maybe it needs time to take effect) but not arena ranks of each player proportional to their power level.
Also, think of this, if they will remove all inactive players in arena in the rankings, they will remove not only high level players with strong teams but will also remove low level players with weak teams. This is why I always think of removing inactive players is the solution.
They cant just remove strong teams in lower ranks in arena. What if the player is just early game but whale too much to have strong team to start climbing arena? They cant just push this player to gold automatically. And it will not be good to whales as they will not be able to rank up their hall easily as they will face strong teams right away without experience in arena. This will make spending in the game not favorable to them when it comes to arena.
Arena is a ladder. Whether you are strong or weak, early game or end game player, you will still start at the bottom or be push to the bottom.
One fix they could have done is to remove arena missions in arbiter quest. A small problem here is some players will not have to be competitive in arena if there are no great reason to play arena when you are early game. They probably want a balance number of early game and end game players playing in arena.