Sejuani is in a really toxic state right now.
Sejuani currently has the highest ranked winrate in every elo aside from Masters/Challenger:
Playing against her is frustrating because she is a really strong ganker with mobility, tankiness, CC and damage BUT unlike her popular contemporaries in the jungle (Lee/J4/Reksai/Vi??) she scales incredibly well so it feels like you're forced to play safe so she doesn't gank you but at the same time you're punished for not snowballing yourself by having to face a late game teamfighting monster without a strong advantage to overpower her team. Her ultimate forces multiple members of the team facing up to her to take Cleanse/buy QSS/Banshee's Veil to not automatically lose teamfights (they still have to deal with a huge high damage tank gapclosing into their team). I never have fun playing against her, It's too difficult to outplay her or exploit a weakness she has like any other jungler and I think her winrate speaks for how overtuned she was with her recent direct (and indirect buffs).
When is Riot going to deal with her?