@Riot: Sandbox Mode, Casual Game vs. Sport, who benefits?
https://www.youtube.com/watch?v=_tdrx3Fohmc
Sandbox is actually very important to both the casual and sport experience in League of Legends. MOBA is a difficult genre to get into. If casual players have an efficient and fast way to learn fundamentals, it might even decrease toxicity in the game as more people reach "baseline" skill level, and reach it faster. It will not add to the already high barrier of entry, but help alleviate that.
Sandbox in itself is also another attraction for the casual playerbase, because it has an appeal as a "toy box" where you can instantly create any kind of scenario you want, and just fool around by yourself or with your friends.
No matter what you think League is, Sandbox provides great benefits to every player.
Riot, please stop overthinking this issue, do what is right, as players and developers have known for over a decade!