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The Argument that will Never Die
One of the biggest debates that have been going back and forth throughout the League community is the question of balance. Players have both commended and criticized the Riot Games balance team for their respective nerfs and buffs to certain champions. The problem is that most of the player base are casual players, while only a select few make a living off of this e-sport by playing in the pro competitive league. But the competitive league has a lot more exposure to the general public, even though it's mostly the general public that is playing the game.
One of the popular ways that players decide to play this game is to get really good at playing one champion. It's been commonly advised by analysts, coaches, and pro players to practice in order to master one champion, and that it would help casual players climb the rank ladder easier than the traditional way. But there are certain champions that are very strong when played at the highest level, but that is not the majority of the player base, but the Riot balance team decides to nerf champions in the interest of the highest competition, making it very difficult for newer players to do well with these champions.
Kalista, Poor Baby
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This champion is the trophy example for why this game cannot be balanced for both newer and pro players at the same time. Kalista is a Marksman champion that is uniquely mobile and cooperative with the support that she is playing with as her Soul-bound Ally.
Her abilities in itself are very powerful and unique, as she gets extra bonuses if her soul-bound ally is nearby. Furthermore, one of her abilities, called Rend, where her auto attacks pierce the enemy with spears, and can be re-activated to pull all of the accumulated spears out at once dealing proportional damage based on the number of spears that are impaled in her target. Lastly, her ultimate ability, Fate's Call, pulls her soulbound ally back to her as a soul, saving the ally from a potentially dangerous situation. She can re-activate the ability to toss her ally back in a direction, knocking up any opponents hit in the process.
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Kalista has faced a number of nerfs patch after patch due to the strength of her kit in the competitive environment. Her bonuses when she is near her ally are way too strong, and her Rend ability is ridiculously strong because the spears get impaled in objectives too, such as Dragon or Baron Nashor. They can be infinitely stacked, thus making it hard for the enemy team to fight for the objective, as the total stacked damage Rend can reach numbers higher than the Smite damage. Lastly, her ultimate Fate's Call allows both Kalista and her support to play aggressive while avoiding an over-extension by just ulting her support out of danger.
All in all, her abilities' strengths are amplified in coordinated pro play, where their strategic decisions lead to almost an unbeatable laning phase and a difficult-to-beat mid and late game. These nerfs make her nonviable to the competitive league, where she is not strong enough for pro play, but too weak and hard to execute for newer or more casual players.
Other Victims of the Nerf-Bat
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Other victims that have been a nightmare to try to balance are Azir, Irelia, and Lee Sin, as shown above in that order. These champions were notorious for receiving constant nerfs to their abilities in numerous patches. In the case of Azir or Lee Sin, they've been known as mechanically intensive champions with very high skill ceilings. They needed a bit of practice to get the hang of, and it was very obvious between the game play of a 'good' Lee Sin versus a 'great' Lee Sin.
Changing the Game for the Sake of Changing it
This video by long time pro player veteran Yiliang Doublelift Peng very accurately explains why this is a big problem in League of Legends. Previously mentioned, a lot of people spend a lot of time trying to get good at one champion. Doublelift brings up a slightly different issue, where Riot would remake champions and give them a whole new set of abilities. Obviously these players would feel upset if the champion that they've spent a countless amount of time practicing. It would feel like they lost a huge investment in their time, because the ability set that they've been practicing just ceased existing.
The paradox of this whole issue is that you cannot satisfy both sides of the player base at the same time. It is actually impossible to balance a champion around the satisfaction of a whole. I feel that all of the complaints that come out from the community are somewhat justified, but the complaints are never going to stop. If you make a champion too strong, it will see endless play in the pro league, and will establish itself as a dominant pick or ban, promoting a lack of diversity. If they nerf a champion too hard to make it balance for pro play, then the champion will be useless outside competitive play, thus rendering it unplayable for the other 99.9% of casual players.