I would have loved to comment this on the article itself but as I am not the same region as the article, I can't. So here I am.
Why aren't the eternals unlocked with something similiar to a mastery score? For example, say I get level 7 on Nunu. After I hit level 7, for every game I play (or win) I get another score in addition to the mastery score. Name it "The eternal points" for now. These "eternal points" would then be used to unlock the different stuff the eternals update would have to offer. Like the flex mastery emote and so on.
Wouldn't this show much more about the skills on a certain champion than just purchasing it with rp? Because even a ran over monkey can purchase stuff with rp. Brilliant way to "Show off skill" btw.