It makes more sense in the context of a world where everything is comprised on a fundamental level of a balance of the four elements. We just don't live in that world.
I do hate it when games have all these elemental stats, and then just never actually use more than 1 of them for anything. If you use 4 elemental types, there should be at least 4 different types of enemies that are weak to each respective element. C'mon.
I was quite pleased when I discovered that debuffs worked on bosses in Octopath. I think FF12 also just gave bosses resistance rather than immunity, so the debuffs would work eventually most of the time. Been a while since I played FF12, though, so I might be misremembering.
Reminds me of the Pokemon Master in Super Smash Bros. Brawl. The three Pokemon had weakness for fire, grass and water.. But of all the other characters in the game, there are a ton of fire attacks, zero grass attacks, and maybe one or two water attacks. So it basically amounted to a debuff for Ivysaur.