If, somehow, you could give every animal on Earth boosted intelligence, cognitive function, etc, would it be unethical/selfish not to?
If morality involves concern for the interests of others, including the protection and promotion of their interests, it might appear obvious that conferring higher cognitive functions on every animal (ourselves, too) would mean promoting their interests.
But it is not at all clear that this really would be the case. I mention just two points :
(1) Where inherent conflicts occur between rival species (predators and predated) higher cognitive function might well make the conflicts sophisticatedly more vicious.
(2) Unless our moral behaviour is improved in pari passu (in step) with higher cognitive function, we may just end up with more intelligent and subtle ways of inflicting greater harm on one another's interests.
You can't isolate one aspect of animals, their cognitive function, improve it, and without changing other aspects expect the result to be beneficial.