Here's some feedback if you're interested.
My issue with Eternals right now is that when you achieve a milestone for Eternals, it doesn't always correlate with having a big moment in game, and I think that's a major failure of the system.
Here's an example-- Braum has an Eternal that measures how much damage you have blocked with his E. I don't think this is a good Eternal because I don't care how much damage that my support Braum has blocked with his E over the course of his lifetime playing Braum.
If you told me that my ally Braum has blocked 400,000 damage with his E, I wouldn't know what that meant because there isn't any context as to how many games he has played with Braum. If he's played 400,000 games of Braum then I would be very concerned about his gameplay, and if he has played 1 game of Braum I'd think he was the best player ever.
I think this is the crux of the issue with Eternals. Because I don't care about my teammate's Eternal stats, I don't care whenever they show up. Imagine, for example, a game where an ally Braum player is having a really rough game. He's 0/10, he's really struggling, and he's single handedly costing us a game. We get into a big fight, he makes a mistake, E's in the wrong direction, and throws the fight, but he manages to block just enough damage that he gets a milestone and everyone sees it. That's not a big moment, not for him, and certainly not for the team. And I think achieving a milestone should be a big moment for everyone in the game.
What's my solution to this? Simple-- make Eternal stats track single plays, instead of life time acheivements. In other words, make them independent of number of games played. Instead of tracking how much damage Braum has blocked with his E over all time, why don't we track the most amount of damage Braum has blocked with a single E? That way, if you tell me "Braum has blocked 4000 damage with a single E," that's impressive no matter what. It could be his 4th game or 40th or 400th game on the champion, blocking 4000 damage with a single skill is impressive as hell.
This also makes achieving milestones memorable for everyone involved. That teamfight where Braum stood in front of MF ult and single handedly saved the fight? His contribution and acheivement is immediately recognized with an Eternals shoutout. Acheiving that milestone is a memorable moment in that moment.
This proposed system makes Eternal milestones mean something every time they pop up, since it makes Eternals about celebrating good plays instead of lifetime stack trackers. Because while I don't care about my teammate's lifetime stats, I do care about his individual good plays in my game.
Does that make sense? It makes the Eternal milestones mean something other than arbitrary tally marks.
I think literally any Eternal can be made cooler and more fun by doing this one exact fix.
Instead of "Amount of damage Poppy has blocked with her Shield," you can do "Most amount of damage Poppy has blocked with her Shield in 1 minute."
Instead of "Number of champions hit twice by Death Ray twice" for Viktor, you can do "Most amount of champions hit twice by Death Ray in 1 minute."
Instead of "Number of champions hit by Void Ooze" for Kog'maw, you can do.... "Most amount of time enemy champions spent on Void Ooze within 1 minute." (this one is kinda lame...)
But do you see what I mean? Instead of seeing "Poppy has blocked the 1,000,000,000th damage with her Shield!" and thinking to myself "eh, whatever," I could see "Poppy has blocked 700 damage with her Shield in the past minute!" This likely occurred during an extended teamfight, and I could be like "Wait, exactly HOW MUCH damage did she block??" That's so much cooler than just an arbitrary big number.