Aside from accepting Blizzards balance team hand-me-downs, they refuse to push against the meta to make this game less toxic and better balanced.
Okay, lets start here - You need to define 'less toxic'. I'd argue that league has one of the best systems in place to deal with toxic players. Hundreds of people are involved in the design and balance of ANY of these games - World of Warcraft, League, or DOTA - They are all balanced and playtested by large groups of people. You really don't have enough information to blame anyone directly, besides - its just rude to do.
The best example is ADCs. Since season 2 ADCs are the main carries of the game and they revolve around primaryly right clicking. Instead of nerfing the ADC role and forcing it to go to a more utility role (Which gives it more diversity and a better basis for champ creation since giving a range AA champ CC or mobility won't break the game) they INSIST it has to be that way.
Every champion in the game right clicks, its a basic function - It's a fundamental action of how you play the game. Just like how much champions press 3 keys to 'win' or score a kill. it's how you play the game. ADC Champions are pretty diverse at this stage. If you want an all-in burster? they have those, you want a nice dance-y juke type that wins trades? they have those. You want a stand on the outskirts and poke champion? they have ADCs that do that as well. The main thing the marksman does is that it 'generally' scales better than most of the other roles in the game, this is primarily due to Lifesteal, making them harder to kill as the game pulls forward and thus a bigger threat. There are lots of 'Utility' ADCs, take a look at Ashe, she has one of the best CC abilities in the game, a great snare-type kit and is just awesome support in general. There's a reason they say 'Support-Ashe' when she gets robbed of her kills and goes on to be an amazing support-type kit.
If you are complaining that ADCs are not diverse enough, I think your confused or lost :(
IDK why an all melee or mage comp scares them so bad but it does. Anyway, they push ADC and mobilty creep agendas and therefore can NEVER balance it. Fix ADCs fix the game (more champs will be viable when ranged right clicking isn't the most important part of the game)
At this point, I'm having a hard time understanding, but Mages have a firm place in the game and have for a long time - S4 has been AWESOME to mages. Period. Right clicking is always going to be a fundamental action that all champions will be using, sure, its more important for champions that use Auto Attacks to deliver their damage but that's just the basis for the design. It requires good positioning and a fundamental knowledge of how the damage will play out.
If there is one thing I could take from all this - I would like to see a few more potential 'melee marksman' types in the game. Master Yi and Yasuo do a solid job as far as that goes, but it would be awesome to see a dedicated melee ADC.