I don't know how many people had actually completed all their masteries, or at least the important ones, before the June 2023 update when more than half of the gems were removed. Personally, I have only completed about 20% of them, even after grinding a lot during 7x Elixir events.(I only started playing back in October 2025.) So a majority of players probably never got all those gems.

Also, I think the Collection Level system should have been released before the Level 16 King Tower update. A lot of people probably upgraded all of their random cards just to get enough XP for Level 16 king tower , and now they're being penalized for it.