Season 8 is the worst season in League History.

To add on to what this man said, generally every tank has been underpowered and thrown into the trash can, especially in jungle, with few exceptions such as Volibear. Season 4 5 and 6 were assassin meta, and i guess Riot didn't learn their lesson and decided to make the majority of assassins, and generally all high mobility champs are extremely overpowered, (Nocturne, Ekko, Hecarim, Azir, Warwick, Volibear,) with Volibear being only Tank who is without debate overpowered at the moment. I guess since Tencent took over Riot we knew it would all go downhill.

Edit: When i say tanks i don't mean bruisers. Bruisers are doing fantastic. But the hard tanks are suffering. Xin Zhao is by no means a tank as a commenter said. The only tank I didn't mention ,that i see doing ok in the jungle, is Dr. Mundo.

If I had to choose what season was the best, I would have to say, undoubtedly, season 2 and 3.