And it's in our nature to see it that way. That's what I called Kes's age "the chronological elephant in the room".
I think the idea was that the crew of Voyager were supposed to be enlightened enough that they could see past the limits imposed by human culture... problem is, as the audience, we can't (and as someone who's in the business of keeping children safe, I say that's a good thing). And that's why I agree with the initial notion: deleting the Kes/Neelix relationship would have been a positive for both characters, and VOY as a whole. Tom and B'Elanna had their issues, but they were a far better flagship romance for the show.
There was series rewrite I did, wherein Neelix rescued Kes and her father (they were friends of his) because the Father was his friend. He dies of old age soon within the 1st season and Kes starts off as a child actress, then a teen and then by S3 she's an adult and her re-emerging psychic powers halt her aging so she stops there. There were other explorations of her condition, like how she could learn at an accelerated rate to match her aging so she could be a proper Doctor within those 3 years as well.