Arenas Shouldn't be an LTM

Well if they are actually testing for engagement, then making major changes to the mode could be a waste of time if data indicates that there wasn't enough engagement.

If a large portion of the players really do want to play Arenas a lot, then they would play the LTM lots and lots.
If they don't, then even if it were to be implemented as a 'full' mode rather than an LTM, it would likely have yielded the same results.

I'm sure they will work on it a lot, if this LTM shows enough engagement to keep the mode full-time.
Back in  it's previous stages of development, they already had a lot of ideas lined up, but ultimately those never saw the light of day.

It's current state isn't great, but the entire point of the current stage is to indicate those players that want it.
The mode has a lot of problems. Balance-wise it's hell because it strays so far away from the core concept the legends and guns were designed around, which would be Battle Royale. Then we have ranked which was utter hell because players would just manipulate the matchmaker and get matched with each other. Apart from the cheaters, there was no integrity to the ranks at all.

From what I see, Arena's really is something that would need a lot of time and resources to make it better and 'playable', but if too small of a % is going to play it, why would they bother?

Though yeah they should've put in party crasher at least, that was definitely my favourite map for Arenas.