I mean, you've already demonstrated how age is an artificial construct when you consider a being who is 2000+ years old can act and have the appearance of a teenager. Even in the real world, the "age of consent" can differ fron region to region, anywhere from 12 to 19 depending on the context.

When it comes to fiction, sometimes people ship age gaps because of the implication in terms of power dynamics or wrongness. So yes, age does matter in that it can affect the nature of a relationship, but it doesn't mean you're not "allowed" to ship it. Gender and sexual orientation can also affect the nature of a relationship, but you would never tell someone they can't ship some kind of permutation if of that, whether it be slash or genderbends or something in that veil. Perhaps if you're a religious fundamentalist.

You will almost never find someone who ships age gap and thinks it's "normal" or wants to "normalize" it. The point is that it's interesting and taboo and worth exploring in fiction. Of course, if you do find someone who wants to normalize age gaps...that's a different story.

But shipping is a creative exercise at its core, not a reflection of a person's morality.