Free to play games fare better when there is some interaction between players. Basically, the game is free so that it gets a nice playerbase, but has some in-app purchases that can make a portion of the players "feel superior" to the rest (being pay-to-win advantages or cosmetic items).
In those games even the players that will never pay anything have some value just by playing because the paying ones will have people to play against. Some of this paying players spend astonishing amounts of money as there is generally no limit to how much you can spend on these games, or if there is it's in the thousands of dollars, so they normally rely on making money out of these big spenders.
So you can't really compare this to LoL, nor to most other f2p games of the same kind since they're generally not single player (even single player ones will have a global ranking of some sort).
I personally think it's probably not the best choice but I'm sure whoever made the decision has more knowledge about it and knows what they're trying to achieve. It would be interesting to know the reasoning behind the decision.