The ARR primals, as old as they are, are some of the major classic summons that Summoners have historically had access to. Shiva is a special favorite for many. Anyone's who has played FFX recalls our first iconic summoning of her against Anima, or how in FFXV her corpse as a giantess was a landmark of the imperial snowfields, and her subsequent intervention during our fight with Ifrit where her kiss froze and shattered him. A lot of people have grown close to these key summons after seeing them in so many games, and thus there is a reasonable sentiment that they should take precedent over more outlandish primals like Susano, who quite literally popped in and out of nowhere within a span of 10 minutes.
However, I would like to see the primals unique to FFXIV be made available to us in the future. But if I had to pick between Shiva/Levi/Ramuh or Susano/Lakshmi/Ravana I will absolutely side with the classics over the throwaways from back when trial fights were built around monster-of-the-week situations in every instance aside from final bosses.
