OP like it or not they're two games within the same genre and they're among the two most well known in that genre as well. Never mind that it's far from unusual to find players who have played both. The comparisons are never going to stop.

Just because these games have taken quite different directions within the genre does not mean it's silly to compare them. It actually can lead to some interesting conversations to note how two completely different dev teams approach similar types of things.

As for how old they are, it's a bit meaningless at times to point this out because while WoW started far before FFXIV, WoW is still releasing new content and it has gone through some very significant changes since its initial launch. It's not as if the game has stayed mostly the same for 15 years. It is hugely because of this that the demand for Classic WoW became so high. Retail (current) WoW is so far removed from the days of Classic that they're different games at this point. As long as both WoW and FFXIV continue to release new content in similar time frames and dates, comparisons between the two are valid.

And personally I think both games would benefit from taking elements from one another. They each have their pros and cons, and each game does something better than the other.