Why is Gnar so weak atm?

So yeah, why is {{champion:150}} so weak right now and why he has been weak for several months? I dont remember him getting nerfed or anything, and its tank meta so he should so fine thanks to his W. Suddenly his LCS playrate just dropped to near zero and I rarely see him in soloque. Also his win rate is still bad, the small buff he got recently wasnt enough. I actually used to main him but switched to {{champion:41}} because I realized GP was just way stronger and a bit more fun too.
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