Lack of Counterplay
I think Riot has made a mistake with removing or severely changing champions with little counterplay. Specifically Talon's E Abilities with little counterplay is what defines good players from bad players. A good player with not allow an ability with little counterplay to affect them or will respond quick enough to change the situation.
Chess is a very balanced game, but most chess strategy revolves around moves with little counterplay: Forks, Pins, Forced Mates etc. A new player may know how to use the ability but will struggle from preventing those situations. On the other hand, a Grandmaster will have no problem finding forks, or pins or a forced mate, BUT they will also be able to predict and find a solution or avoid the situation altogether.
Balance is a difficult thing to do, But there is more to balancing than just leveling the playing field, and this is what Riot lacks the most. A lot of Riot's changes are usually to tone down a champions abilities, to scale down the level of "OP" that a champion or ability has. The problem with that is it make the game very stale, and repetitive. If Riot wants to make a game that is constantly exciting and continuously changing and molding, they need to embrace Perfect Imbalance.
MTG does a great job with it's "Jedi Curve" and I believe its what makes a game last forever. This is a good link if you're interested - http://community.wizards.com/content/forum-topic/3499686
I really love Riot's ambition with its recent champions (Yasuo, Gnar, Lucian, Aatrox, Viktor Rework, Sion Rework,) The problem is that these champions are good at TOO many things. So please, Riot stop making ranged,melee champions that have cc, mobilty, tankiness, and damage, and start making champions that have inherent weaknesses and crazy strengths (Attack ranges, cooldowns, Mana costs, no escapes). After all
When everyone's super, no one is - Syndrome
for example has good mobility in his miniform and massive tankiness and cc in his beast form.
However both forms have also extreme weaknesses(mini is squishy and beast is really slow)and you can't even use these forms whenever you want.
Enemies can see "oh you are about to transform,better keep my distance".