As a casual player who works full time, I do not have time to re-learn champions. I have a small handful of maybe 5 or 6 champions that I play decently well.
Since starting October of S5 ... You guys have re-worked nearly 1/2 of my champion pool.
Xin - 633,040 mastery points prior to rework .... I hate the new xin - so iIdont play him anymore.
Kayle - 117,915 mastery ... Do not like how she plays now - and do not have time to re-learn her ... so I am done with this champ now.
Morgana - 157,649 mastery .... Do not like how she plays now - and do not have time to re-learn her ... so I am done with this champ now.
I now only have 3 champions left to play in ranked. 2 Jungles and 1 Midlane.
By constantly changing champions / the game in general ... you make it impossible for casual players to keep up. So we end up just falling off and moving to other games.
Maybe instead of re-working champions ... you should make new champions .... or make a legacy option to allow players to use the old version of the champion.