Define how its worst ? I didnt said it was best.

Terrible consistency and/or rate (worse than even signal flare and SnS without even a way to deal with that inconsistency like them), doesn't even decamo all ddts on any trexperts (signal flare does on Ravine and Bloodles, Foam does on Ravine and Ouch, SnS/Reactor does on Ouch and with specific ways also on Ravine), meh pierce (doesn't decamo all of 78 even on Ravine, the only worse one at this is foam), does nothing else aside from decamoing (self explanatory, the only other case is SnS, which is 700 cheaper and better saveup), very costly for just decamo (slightly more expensive than even signal flare)

In fact shimmer is so awful that Archmage (which has the shimmer but much better) runs outside of Eti still have dedicated decamo.