riven's rework is already said to be very experimental and they're willing to take it down

because her mains don't like the change, even if it's a potential buff to those who have mastered her with the damage increase and non-execute ultimate

in the time i've been playing this game (around shortly after Jinx's release), i have not seen the same courtesy shown to other reworks, except for Lee Sin. (of course)

Cassiopeia players hated the rework that completely altered what she was. All they asked for was a grace period on her E's reset to make her combo smoother; what they got was an unwanted rework that turned her into this awkward, time-based carry. A myriad of poor design decisions were forced into her kit while overloading the hell out of one ability so that she'd be "functional." Before, she was able to at least play somewhat flexibly; Q max was a viable option, and her E spam was, too. Riot decided to neuter her poisons in favor of making her E completely central to how she plays, failing to realize that, from what I've seen, most players would have MUCH preferred her being THE premier DoT mage, someone who can really satisfy that theme of a poisoner. Riot did much worse than not keep up with player concerns; they lied about saying they would, and then the man notorious for it now, Stashu, disappears for months at a time. After a brief period of being too strong, she is now both bland AND undertuned.

Mordekaiser mains protested the drastic changes that completely alter how he plays and feels. All of the experience previously mounted up is gone; you can no longer play him in solo lane without being a detriment to your team. His skill maxing order has been made less diverse, his build path is less interesting (build tank or die) and he is no less frustrating for others to play against as evidenced by the constant complaints about how strong he is. He is now a shell of his former self who can't even enjoy a game in the pro scene because the one ability he's centered around using for damage is ridiculously overtuned at the cost of the others (notice a trend?). Riot ignored all criticism regarding it and it took weeks before the person who spearheaded it even bothered to reply to complaints. Currently, Riot has not announced any future plans to satisfy the people who prefer his old, much more varied playstyle.

Just because a champ is unpopular doesn't mean that you should feel welcome to throw their rare but beloved designs out the window in favor of some grand vision that will magically raise their play rate (the exception being extremely archaic designs that have proven to be genuinely bad for the game -- Warwick is sad you shelved him). Please don't rework them in ways that are the exact opposite of what their communities ask for, then refuse to change more popular champions because they have a larger group to flood Reddit and Boards with.