Well that would be the same with you with your made up sense of authority dictating everything is what happens when it didn’t. Wall’s attacks reach continent level with Etherion, and does not change that Spriggans scale to one another. They do because Zeref scales to Phoenix and supported by people who are aware of his existence and know of his works, Acno scales as well
It's also hard to explain for some ppl
The way S12, Zeref and Acno lost is unbelievable set of circumstances which manga never knew before.
Hiro actually made them strongest enemies in story, but did not spend relevant screen time on them (well, it's 14 ppl total = 12 + Zeref + Acno),
In afterwords Hiro said that redactors suggested him make 6 spriggans. But he kept 12.
But the way they lost doesnt mean their feats are insignificant and they're weak.
On other hand current enemies (like Dragon eaters) look far more weaker and have more casual and non-astonishing abilities).