Having to relearn a champion has the same effect as them saying "We know you lived through this fantasy, but that fantasy has come to an end because we thought it was unpleasant. So we're taking your vampires/zombies and giving you muppets". It's devastating... If you want something new, find a new champion with different abilities. That was actually part of Riot's mission statement in 2010, that new champions came out every 3 - 4 weeks to keep the game fresh for those who need new things to learn.
People who enjoy a champion like the feeling they get from everything that they've practiced and most likely done ranked with. Having played since season 1, when Karma was turned into what she is now, I had to stop playing her for months...at a time I was playing 4-6 hours every single day. I used Soraka since day 1 and Cassiopeia the day she came out.
Do you know what it's like to have to stop playing your favorite champion because their gameplay went in the opposite direction, their ratios were changed on a weekly basis due to Riot not knowing how effective they were, deciding what to rank first changing regularly because effects too are removed biweekly, nobody caring to read about the changes and hence not being able to react to what you're doing?
I've actually stopped playing LoL, but I come to the site to see the newest updates and to comment. Now I just do Overwatch and Smite on Xb1 because my comp is essentially outdated. But the lingering memories I have of 5 years of playing is, "wow, I had these amazing games when I was doing my best. it's a shame that I couldn't relive that if I were to join back today because of the rework happening. So I would have to move on to so-and-so champion...eh nvm I'll stick to something else." It's weird to keep that mentality, but unfortunately that's what stuck around.