Riot, I feel like you guys completely missed the mark.
This pre-season, Riot stated that their goal was to fix diversity. In doing so, they wanted to give players choices that can change how they play the game, both pre-game and in-game. However, what has occurred is the same thing that happens every year: The same strategy gets played every game.
With masteries, they gave us "Keystones", masteries designed to change the way you played. Want to be aggressive? Go with Ferocity. Want to be more utility based? Cunning. Tanky? Resolve. There are also sub-categories for each as well. With masteries, however, classes are making the same choices every game. ADCs are using Warlord's Bloodlust, Bruisers are taking Fervor in Battle, Mages are taking TLD if they are spammers or DFT if they are burst mages (Though according to the community, every mage and assassin is taking the TLD, however I have yet to see that), and supports and tanks are taking the offesive masteries because the tanky ones aren't that great. Choices aren't being made. It is always the same.
Items fall into this category too. ADC items got reworked and more were added in, but the same items are getting played. If you have long range, Rapid Firecannon every game. Burst carry? Statikk Shiv. Lots of attack speed? Hurricane. And the Armor pen items are the same, no one builds the Mortal Reminder because 15% more damage against everyone is better than grevious wounds (With the GW changes. Before it would have been great).
The choices that are being made are not based on "What should I accomplish this game/How do I adapt?" it is still "What combo works every time to best, and still works better than the combo that SHOULD work in a given situation?" and that is not what you want to accomplish, Riot. I know this. I have watched you for 3 years now. This isn't working, and I blame items and masteries. I hate to do this, but look at Heroes of the Storm. They have no masteries, no items, nothing of the sort. What they have are talents, and you take them as the game progresses. AND THEY ARE ALL MEANINGFUL. I have never looked at a talent and thought "I will never use that ever" because they are all useful. Those are meaningful choices. That's what you are aiming for.
This game is fun, I love it. We all love it. But stop trying to make things meaningful and stop trying to make diversity. With the game you have designed, that isn't possible. Its okay that it isn't, but stop pretending that you can "fix" it.