I mean this is gonna get buried at this point, and I'm not here to debate the state of Yuumi (I agree with most the points anyways).
Disabling champions is a joint venture by esports and Design. It's actually primarily Design's call on whether a new rework is disruptive enough to be disabled for early patches (see midscopes, new champions, etc).
My tweet was more directed on that Champs/SR gave the same feedback to esports to disable these champions for MSI, and that the displayed graphic showed a different story that funnels more negativity into the topic.
Even the post-release results tell a similar story, even though the details and lead-up to each one is different. These champs (and a lot of new releases) are highly risky for competitive tournaments, ESPECIALLY global events.
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