See, I never said that fish does not have feelings or that fish have feelings. I think it is meaningless.
"Feelings" is an abstraction that makes it easier to explain human behaviour. With fish, asking questions like "does it have feelings", "does it have free will", "is it conscious" etc. is just the same as asking the same questions about machines: it does not help you to make any decisions about how to interact with it, so it does not matter.
So, to extend the question I asked before: Does that mean because we cannot ever really know what goes on in another human's mind, does that mean human "feelings", "free will", or "consciousness", are meaningless and does not help us make decisions about how to interact with other human beings?
"Feelings" is an abstraction that makes it easier to explain human behaviour. With fish, asking questions like "does it have feelings", "does it have free will", "is it conscious" etc. is just the same as asking the same questions about machines: it does not help you to make any decisions about how to interact with it, so it does not matter.