Then again perhaps giving them enhanced cognitive capabilities would only serve to make existence worse for them? In which case, giving them enhanced cognitive capabilities would be morally worse than leaving them as is.
Kind of your moral question but in reverse.
As it happens, I am perfectly comfortable with the idea of intervening to help animals in more cases than we currently do, and if I had to guess what one belief we have now that will be regarded as appalling by some future generation, I think this (letting nature run its course when it leads to animals suffering) could be one of them.
Becoming sentient on an already developed industrialized world seems like it would be awful, though . I like to think there are many paths where a species could be welcomed & supported well, but it's hard to imagine that happening on our present earth.
We should be careful in case someone decides to try to uplift us.
So that may not be an argument in favor of it being the moral choice.
A lot of discussion on the problem of evil is quite obscure but worth reading if you're in any doubt about all of creation being a fundamentally excellent thing.