My attempt at explaining low LCS diversity.
I'll be comparing tanky champs here. Rek sai and gragas vs poppy and maokai
Two are generalized and two are specified to being wardens that protect their team. The generalized ones are the high pickrate ones. The reason why they are such high pickrates is this, In the scenario of a leblanc diving on your back line with these different champions, rek sai- knock them up gragas- stun them with E and ult them away if necessary poppy- E and/or/ R(W too) maokai- W Q (with R active).
They can all peel fairly well, less so rek sai, but she trades that for her mobility and her ult. But when it comes to engaging... rek sai- flash knockup/tunnel knockup gragas- E flash R to knock someone into your team poppy- no safe and reliable engage. Maokai- no safe and reliable engage (too short range)
In this case you would always want to pick rek sai and gragas. Why not? They have close to the same peel as poppy and maokai, but they have much better engages. (this isn't even getting into how OP gragas is in general).
this is my pretty ham fisted way of trying to explain it but here you go. if you want a better player to try and explain this + more here you go https://youtu.be/XEmH1xQKQQE https://youtu.be/cmZ8BslKv18
