The Four Lords actually aren't primals, but they are very primal-like to the point where confusion is understandable. They're kinda the closest you could get to a 'naturally-occurring' primal, in that they have that level of strength just from being alive for so long that they collated that much aether, but they aren't primals by any actually useful definition.
But yeah, to me as someone who isn't a fan of its comedy, Hildibrand is huge mostly as a place where they play with story ideas before they hit 'primetime'--sometimes stuff that never even gets a full, 'serious' story for whatever reason. On top of Enkidu being the first 'unintentional primal' as we'd see later from Susano, he's also the first primal we learn is actually based on a real person, before we learned the same thing about Garuda and Shiva, and ARR Hildibrand also gives us the true story of Ul'Dah and Sil'Dih. His Stormblood questline is the only one that really goes into detail on Hingashi politics, as well as being the first proper presence of Thavnair beyond materials and lore. Hell, EW's has already stepped up to the plate to provide some further detailing on stuff we thought was done.
Not only did we get a touch-base with the First to learn how people who weren't important enough to appear in the MSQ revisit are doing, but it also gave us some level of explanation and cheracterization for Dr. Lugae, who I think we all sort of wrote off as an unexplained weirdo.