It depends when you started playing League ... I remember countless Ryze reworks with a bunch of them failing. Karma rework honestly I wouldn't consider a success but I wouldn't consider it a failure either it's just kind of neutral. I do agree though that some people are just scared of change.
I've played since S1 and Riot have definitely messed up reworks and even if you look at their current record they still haven't been resoundingly successful. In fact I can't think of a rework that was successful on its first go, it almost always had to be patched and sometimes reworked again, does that mean they don't fix it eventually or get closer to where it should've been, definitely not. Riot does a fairly good job but that doesn't mean the community knowledge can't help them get to that spot quicker.
Like I said before when you have people who main a champion for countless amounts of games with hours of experience in many many situations then that knowledge if they're willing to share it can be very beneficial when considering the best routes to rework champions and overall can make their reworks MORE successful. Does that mean Riot should listen to every criticism, no because not every criticism is valid but to dismiss all points even the valid is not beneficial to the game or company.
Look at the Heimerdinger rework when it was released... it was so OP it was played top lane with hilarious success even in the professional scene and then it got nerfed to where it is now but on release his big turret did as Phreak would say "Tons of Damage". Another example would be the initial Gragas rework which most would probably consider a success in its current state but on its release it was a whole different story. Sometimes they mess up the reworked kit entirely or partially for example I think most can agree that Karma's reworked W is more or less a failure, and sometimes they do something silly like change Maokai's ult to follow him which was a great change but it was too good for teamfights and eventually they had to nerf it so it only lasted so long. Actually the more I think about reworked Karma the more I really wonder if it was successful.
EDIT: Now that I think about it what about the Lucian changes they did (the one after they nerfed his attack range) the community and even pros thought it was going to make him horrible then they realized what Riot did and he went from a great pick to a great pick but for different reasons and ended up needing to get his "removal of slows" on his e removed from his kit because of how broken his mobility was and arguably still is. Another example could be champions like Eve, Rengar, and even Twitch, Riot definitely had a bad run with reworking stealth champions.
Now I'm not saying I hate Riot or think they are doing a bad job but I am saying that they don't always know what's best for the game because they don't always know what we the players are going to do with the changes they bring. I think the biggest success they had was the rework on the support role though.