Well, you can look at that from two view points:
A) You're right. They need ppl to watch LCS and Worlds, so they have to make the game visually appealing. Also pros must have something shiny and good looking to play. Hence - mechanically difficult champs with tons of damage, and flashy-plays potential. Maybe one or two broken champs to add some "fun" factor and PEEENTAKILLL potential. Views attracts sponsors, that pays real money. Not those few ppl who buys tickets and pay 10€ per 6 months for one skin.
B) You're wrong. If something is broken in low elo, because players are bad and can't learn how to deal with it, that doesn't mean the game is broken. If Platinum 1 Vayne can solo five silver 5 players, that doesn't mean vayne is broken. It means those 5 guys suck and should L2P. If something's really broken, it would enable bad players to win against better players. And winrate of broken champ would be equal or above 53%. If that's not the case, game is all right.
PS: Everybody knows RIot only listens to whatever gets most likes on Reddit and little bit what NA players says. Because every other server doesn't make real money, so they don't get to decide what's gonna happen. Classic business model, you should be used to it by now. Even Blizzard does it.