Why do I feel like this is the least diverse league has been in awhile?

People said that at the beginning of season 5 too.

Remember when jungling was basically choosing between rek sai and jarvan?

In general? Or in competitive?

It has a lot to do with the rigid current meta in competitive (always laneswap and early turrets - those simply give too much gold currently) and a few of genuinely too powerful/overtuned champions and items.

Champions: (was nerfed on 6.2, though) , possibly (I think her wave control is too strong, currently - have Q deal reduced damage to minions to reintroduce that intended weakness),

Items: (the enchantment)