I agree, fill it out. However don't expect anything out of it.
There has been a very similar survey a few years ago at a mid-sized European legacy carrier. Supposedly a very cooperative minded airline with a similarly cooperative union.
The survey's result was never transmitted to the employees, apparently the outcome was not to the management's liking!
Irony of the situation: Today the contract with the pilots had been cancelled and the union has filed an official juristic complaint ....