It's too sad to think of the finality of culture, but this is the least I can do. I think it's great that some Ainu are relearning the language - it's such a strong cultural bond.
I'm white but I work with a Coast Salish language that the tribes are trying to bring back from extinction. Indian children were forced into boarding schools and beaten if they didn't speak English, so a generation grew up without learning and the last L1 speaker died a decade ago. So much was lost, but linguists and elders wrote down enough that revival is possible. It will take hard work and determination for entire tribes though, so it may never recover except in ceremonial usage.
Not every society has produced things of equal value, and it's not particularly offensive to notice that.