I don't mind the Blue Essence system... But it needs improvement.
As the title says...
I honestly don't like how you can only get it via capsules (or hextech chests/champion shards); I feel like blue essence, if anything, should also be earned by first win of the day (same amount of blue essence you receive as xp - example: 575 blue essence a day).
I also would love the mastery upgrades to return back to its original costs, as it is a tad bit expensive.
The only flaws I see in the blue essence system honestly.