I like Arenas. So does my kid. We probably play more than 50% or more of our time there. I started with Season 7, but barely touched the game till Arenas.
It's a better "basic training" then the Firing Range, and helps you get better at the game combat basics.
If anything, I think non-Ranked Arenas should be the only mode you can play until like level 50, just so people learn some basic fighting before trying to hot drop Fragment all the time.
One thing I have seen from this current LTM though, is that Arenas might be more interesting and less snowballing then now if they made a a 3 v 3 v 3 and updated the maps properly. Right now, who ultimately wins is usually determined by who can rush materials for the later rounds.