Kennen: Why is Slicing Maelstrom gimped at early ranks compared to other teamfight AOE ultimates?

How I used to love to play Kennen. He was my favorite champ in the game to play for the longest time. His time in the competitive scene back in years past though led to him being Nerfed hard and never really touched much since.
I'm wondering why Kennen's ult scales the way it does when similarly strong AOE ultimates are not limited in terms of who gets hit, let alone stunned by it. (Morgana for a popular example in terms of ultimate/utility from
I could live if his ult could at the least be a little more reliable when it's distributing bolts but would love to see if at any rate he could be looked at for some tlc given how the pace of the game has accelerated and hitting 16 before big 5v5 teamfights doesn't happen all too often, especially given how league is tuned right now.