Everything wrong with League of Legends
I'm going to use Aatrox as an example to bounce into the problems I see with the game.
1)Build paths. The game is quite unfair with how well champs sync with items. There is hardly any question on what to build on Yas or Sej, but Aatrox for example, can't build straight damage or straight tank, or he will suffer. His heals scale of of missing HP, which means building health is useful. But his abilities scale off of AD, none of which do any good without attack speed. If you were to take a level 10 Aatrox with only ONE complete item and 1v1 Rift, guess which item lets him do that the fastest by a good margin? 
So some champs enjoy very clear cut build paths and items that sync incredibly well with their kits, which is why some champs can use
so well, while a champ like Aatrox can't. Another difference would be that if Aatrox builds straight damage he can be bursted down easily, and likely not have his revive up, but champs like Yas can windwall that burst, or at least block it with a shield he gets just for walking that scales off of AD. Other champs also have such shields or blocks or parrys (Fiora, Panth) and they would otherwise be as squishy as Aatrox if not for them. That's why straight damage on Aatrox is very challenging.
2)Escapes and CC. A champion like Aatrox has his only escape built into his only hard CC. This a huge issue, and makes it very tough for him. Renekton, Riven, Yas....many champs can stun or do CC and still have an ability that lets them maneuver and escape or chase. This one of the reasons Aatrox is one of the worst champs in the game. It has nothing to with stats--his CC is linked to a shitty dive. Brilliant.
3)Item compensation. You have all seen it--super tanky champs doing tons of damage while being unkillable. Or super damaging ADC having for some reason extra damage WITH some armor and a revived. What is the point of tanky vs squishy if the items are all designed to try to lessen the difference between champion types? You are a slow tank? Here have a 
4)Champion Bias. Riot doesn't actually care about balance. They care about keeping champs who are popular popular so that it attracts and retains players and generates micro transactions. People dont buy skins of shitty champs who lose compared to broken champs who win.
We have all been taken for a ride. Riot makes us believe this is a game of skill, or that they want it to be fair. Its not, and they don't. If you want to win, you actually don't get to decide who you want to main---you have to play the handful of champs that they like to leave in strong states who can carry.
only have 1 skin where as
(Riot's long loved favourite champion) has atleast 8-9 skins atleast by now.
that have an awesome lore and have weird scalings or are quite outdated and have odd scalings that don't really have a clear item build path as you mentioned.