@Riot how about a compromise on Sejuani?

You can keep these dumb mechanics that came with the rework, but let the overall kit still lead into the original fantasy (a late game, teamfight-oriented diver and not a mid game skirmishing tank). My example that I'd like to put forward as an ex-Sej player;

passive: rework version, remove the frost proc from passive

q: reverted (1 sec knockup)

w: rework version (i hate this version but we'll never win this battle). does magic dmg

e: keep the stack mechanic, remove the melee stacking feature. Now, stacks pop all at once e.g on every enemy instead of a point-click. Deal % of their HP per stack (let's say 3% per stack for now) with a slow that gets stronger per stack; if they have 4 stacks then they're stunned instead. Q and R can now apply stacks. Static CD on champs removed; raise the cooldown

R: stun removed, keep the slow storm.

This revives the old best-case scenario of a 5 man stun but backloads it onto having to be in an extended fight rather than opening with it. In addition, her general engage requires a stronger commitment than simply throwing R into a crowd, which immediately solves the "ult bot" """problem""" that makes her so reliable in pro play and so overbearing whenever she becomes a strong pick. In exchange for this, reducing her ability to stunlock one person, and for getting rid of the melee ally mechanic, Sejuani gets more means to quickly acquire stacks if she plays her kit well.

I think this is a good compromise between old and new kits and this with some base stat adjustments she would be completely fine.