Mobility Creep
Of the 129 champions in the game, roughly 31% of the champion pool has a dash of some sort that doesn't require a target. If we include targeted gap-closers and abilities like Akali R, Alistar W, Amumu Q, and so on, the percentage of champions with non-movespeed mobility modifiers shoots up to 49.8%
If we include Flash, that percentage goes up to 100%.
Compared this to 2009, when the game first came out: of 42 champions (the last champion of 2009 being Nidalee), 21.4% had dashes that didn't require a target, and 35.7% had any sort of gap closer at all (including both "true dashes" and gap-closers that require a target).
So to sum it up, we have the following: ---Between 2009 and 2016, there was a 307% increase in the champion pool size ---Between 2009 and 2016, there was a 144% increase in the percentage of champions with a dash. ---Between 2009 and 2016, there was a 139% increase in the percentage of champions with any gap-closer, including dashes.
Do note that for the purposes of separation between dashes and gap-closers, I elected to count champions who had both types as only contributing to the "true dash" pool. For example, Kalista can dash using her Q, which requires no target. Therefore, she goes into the "true dash" pool, even though the vast majority of the time she requires auto-attack targets to proc her passive dash. On another note, I placed Lee Sin in the "gap-closer" pool, as his Q and W both technically require targets, despite his ability to ward jump being possibly viewed as a self-reliant dash.
So what is Riot Games going to do about this rampant mobility creep? Will they tone it back and cull some dashes from the game? Will they implement turn rates? Will they even address the issue, or will they ignore it and continue to release new champions that have progressively more overloaded kits?
I understand that you have cool ideas and characters and designs that you want to execute, Riot. I really do. As a game developer and visual artist myself, I can understand the temptation all too well. However, please keep in mind that developing and maintaining a game like this isn't just about fun. It's not just about cool characters, or about selling a champion's kit with cool particles. At a certain point, you have to stop trying to forcibly engineer the "fun" that your players have, and instead strive for a competitive balance in the pool.
Let the players create the meta out of a relatively level playing field, where every strength is coupled with a clear weakness. Let the meta shift back and forth as the players' tastes and strategies change, and not because you're shoving it back and forth. There's no need to try and spice up the game and constantly implement game-changing patches. There's no need to work on your patches in 2-week sprints. Chess has never been patched, and it remains a fascinating and ever-changing game with almost unlimited strategies.
Feeling the need to force storylines and strategies onto your players is an insult to them and to your game. You can't trust your players or your game to generate interest and fun on their own, and instead you feel obligated to force-feed paltry imitations of these things to your audience. Please, stop trying to play puppeteer and let your game blossom, gently guiding it as it goes.
tldr you're adding too many damn dashes into the game. do something about them.