Why is Riot biased about their own game?

I really want to know why Riot thinks that shooting themselves in the foot and trading short-term income for possible long term sustainability is a good business model? What is the point of being biased towards some champions simply because they are more flashy (I.E. )

Even if these champions are not deemed "Overpowered" in their own right, they still dominate the game with their mere appearance over the appearance of other champions which can also fill their roles.

I just do not understand what benefit being biased about this game in favour of token favorites actually achieves, I mean sure, it may boost sales and skin sales in the short term but it is just going to annoy other people in the long term and drive them away from the game itself which is bad for business. This is not a problem that is just limited to League of Legends but to all F2P games in general.

Surely, having each champion have clear strengths and weaknesses without this favoritism towards aggressive and generalised champs ( etc) would actually help out MORE in the long term as people could improve with the champions that THEY want to play and not what Riot dictates is the strongest. Riot just seem to be killing themselves and have bought into their own hype way too much.

Its really sad if all they care about is the money and not actually giving a fair experience to all players of ALL skill levels. When a company does not care about their own product, then that creates a terrible experience for everyone.