Lee Sin actually represents good champion ideals when it comes to design
His kit isn't like the average bruiser such as Xin Zhao or Pantheon who is literally just a stat check.
He actually takes a bit of skill to play and has to play well to beat his opponents.
Lee Sin represents better ideals for bruiser design than Xin/Irelia/Pantheon/Jax/Wukong/Trundle because you can still outplay a Lee that is stronger than you unless he is hopelessly ahead, and a Lee that is a bit weaker than you can still finds ways to deal with you without dying, and with the way that Riot nerfs Lee's kit, he is generally going to be a weaker duelist than you unless you were already lowish on health or he was a fresh level 6 with two longswords and a machete, and even then you might still win if you have your ult as well.
is a great example. They are rarely game-breakingly powerful in the meta, but they are so good at so many strategies that they will always work with whatever the strategic meta is. Unfortunately, it's probably unrealistic for that many champions to be like that. But almost every champ is good at SOMETHING, even if what they're good at is a strategy that isn't as effective this season. For example,
is a great early game bully who can dominate most of the time top lane, but his lategame is somewhat weak, since he has no mobility and requires large amounts of defensive stats in order to be in teamfights, preventing him from building enough ad to directly carry - as well as having only mediocre pushing power, also due to his lack of mobility. This makes him especially weak in this season, where the biggest goals are objectives, which tend to be won by teamfights, or vice versa. But if the meta was all about early game dominance - like it was in S2 - he becomes a very useful champion.