If you're in your mid 30s now you'd be in your early 20s when Avatar the Last Airbender originally aired. Since it's a children's show (Nickelodeon), you wouldn't have been in the target demographic, so I don't think that's unusual.
I'm your age and I never even heard of Avatar the Last Airbender. I'm sure my younger cousins know about it.
The claim was that "Frankly... among my generation of roughly 30 year olds, I'd expect Avatar the Last Airbender to have higher cultural impact than 1984 (which was written in 1949)." - if you and I would have been early 20's, that would have made that cohort late teens, so I still find the demographics weird.
I'm your age and I never even heard of Avatar the Last Airbender. I'm sure my younger cousins know about it.