I feel like we had this conversation before, Vysse: it isn't practical, it isn't rewarding, it isn't fun.
Not practical: Balanced 1v1's and Sparring 1v1's teach us dueling and give us a reason to do more than duel in our main towns. 3v3 teaches us small-skirmish dueling. 5v5 teaches us slightly larger small-skirmishes with terrain changes. FFA teaches you how to react and fight in slobber-knockers. The original Maelstrom arena 10v10 at least taught you how to do some form of naval combat. But this arena does......nothing outside of the arena. Doesn't teach anything, isn't useful, feels pointless to join.
Not rewarding: The drawing to arenas is a mixture of honor and currency. The 1v1 arenas give a PVP ring for the top contenders and pots with a good bit of honor. The 3v3 and FFA arenas give a PVP earring for top contenders and pots with a good bit of honor. The 5v5 arena is a perfect example of a failed multi-person arena in that no one queues for it because the honor rewards for winning and losing are laughable. The Maelstrom arenas have coins, but you only get 1 coin if you win, and the daily quests to get extra coins are "participate 5 times", "win 5 times", "win 3 times in a row". So the arena is basically BEGGING YOU to queue up and AFK, potentially screwing over your team. No one wants to queue into a coin flip without incentive. At least the previous Maelstrom arena had some incentive to do more than boat combat, but THAT screwed up the dynamic of the point system because you could win a cannon fight but lose the PVP, and it didn't help that quests wanted players to kill 30 players at once for coins instead of my suggestion of separating the quests into "kill 5/10/15 people" in a progression system similar to the Library kill quests. At least the honor given in this arena is significantly better than the old arena (~150 for the losing team vs ~650), but there just isn't incentive to do it.
Not fun: You hop in a speedboat and drive up to a weapon and roll the dice hoping for a strong weapon that isn't utterly useless. Boat controls alone suck, some weapons just bypass the boat you were aiming for altogether like the torpedo (and sometimes the flamethrower even misses). Teammates AFK because they just get credit participating. The only variation is in what weapon you get, everything else is set so gameplay gets very stale very quickly.
But I've already told you all of this before.