Fire is really nice right now because the +100% eidolon and self-buffs allow it to steamroll current content in a way that other elements typically can't. But keep in mind that Accessory Rank 4 is essentially ONE FIGHT. Just because burn strategies work really well right now, on one particular encounter, doesn't guarantee that this will always be the case. And if one's goal is to sit back and auto-battle, burn builds probably won't be optimal.
Personally, my goal is to make flexible builds that can handle a variety of situations. I'm not anywhere close to my optimal team(s), yet I'm clearing current content just fine. As changes hit like the ATK debuff cap, I'm ready for them. I respect those who make good build decisions, make excellent use of limited resources, and have a comprehensive understanding of mechanics moreso than those who clear content effortlessly through no merit of their own. Why? Because knowledge and experience are transferable, while characters and equipment are not.