My opinion is the exact opposite; I think the Arena mode should be brought back for a limited time only, and should never be made a permanent feature.
When the mode was originally released, it was met with initial enthusiasm, but as time went on and more players became accustomed to the Arena, a number of problems arose.
For example, matchmaking issues have led to an increase in one-sided matches, such as users who don't play Arena that much being put into the same match as heavy Arena players, or players with clearly different levels of skill being matched together, players teaming up for rewards such as badges, and matches being destroyed by cheating issues that have yet to be resolved.
I think that since it has only just been re-released, there are quite a few players who are enjoying it out of nostalgia, but if it were to remain permanently, a huge number of unreasonable and ridiculous problems would arise, just like the period just before the old arenas were removed, and it would end up becoming more stressful for players than fun.
That's why I think it would be better not to make Arena mode permanent, but to bring it back occasionally as a limited-time mode, like this time, when the time is right, and end the play period while players are still enjoying it.
In its current state, where the cheating issues, teaming issues, and even matchmaking issues have not been resolved at all and there are no signs of improvement, to be honest, this mode should never be made permanent.
If they are going to make it permanent, they should do so after solving all the numerous problems Apex has had for a long time, such as cheating issues, teaming issues, matchmaking issues, etc. Well, no matter how you look at it, EA/Respawn will never be able to solve these problems, and they won't even try to solve them, so Arena mode will never be in a good state to make it permanent.
That's why Arena mode is best left forever as a limited-time mode that we bring back from time to time, wrapping up its lifespan while it's still fun and before players start to notice the issues.