Why is race selection commonly mentioned as either not important or of nearly negligible importance by the end game instead of being more of a basis for how the attributes finish out and adding flavor to playing style?

For example, a quick Miqo’te white mage who can stay up to heal longer while dishing out more damage whacking things between spells, as opposed to a little Lalafell who can heal more but isn’t as much help finishing the fight and might fall down if left unattended.