I would first propose that the thing that makes human life meaningful - and also the reason why we have any intuition about anything being meaningful - is because of our capacity to experience good and bad feelings. That is, our capacity to witness happiness and suffering from a first person perspective.

And I think it's this same capacity to witness, which, I think, is also what gives rise to our idea of a "soul".

And so I think the greatest fear and danger we face when considering whether we should accept machines into fellowship with us is, "what if they witness nothing at all?" Because if they don't witness feelings, then they aren't generating meaning, and they really aren't like us in the most fundamental way that we care about.