Sandbox and community toxicity
So Riot's reasoning is pretty nonsensical when it comes to why they don't want a sandbox mode and I think changing that attitude could help with the toxic community environment.
As my example I'll use SC2, which I used to play back in WoL before switching over to playing more LOL. At least back in WoL SC2 I feel like the community was made of a substantial minority of people looking to help. I remember meeting a plat player when I was in silver who came into a custom game with me and helped me fix my game mechanics. I remember improvement being a big piece of the community and streams like the day9 daily being hugely popular. Contrast this with LOL. There are some improvement videos (Fox-something) but has anyone ever had a higher league player offer to help you out who you didn't personally know?
Why? SC2 and League are both competitive online games with an eSports component. The biggest difference is League is a team game and I do not think simply putting 5 gamers in a room must generate death threats and tourette's level cussing. The difference is blizzard made practicing and improving a big part of the multi-player experience. There were custom maps with 20 some odd scenarios to help you work on mechanics, which blizzard supported. By offering the tools and establishing the precedent they made practice and improving a focus of the community. Rarely did I ever meet an SC2 player who felt the need to bad mouth (rare but not unheard of obv, this is the internet) and thread conversations about build counters and mechanics tips were plentiful and easy to find. By arguing that training will create a noob barrier Rito is holding to an environment where players think they would be pro if they could just get a good team (I've asked and had numerous people believe this) and that environment fosters the horrible trolls we have in league today. Offering training (sandbox or otherwise) does not create a barrier for noobs or offer trolls a chance to rage more (like they needed it). It shows that rito is helping you to get better and instills in the player base a desire to improve over rage. Trolls will troll, but if you support improvement you can create a community of players who push past the trolls because they know there are concrete ways to improve.
And to anyone who says "practice in game" I invite you to name any game requiring skill where the highest levels of players did not drill and practice out of game. Go ahead, google search. That game has never existed since the beginning of time. Practice on mechanics has been of cornerstone of competitive success since competition was invented.
To anyone who says "practice in bot games". Bots are atrocious. Horribly predictable and easily beatable they offer no real training outside of those picking up league for the first time. Playing against a child in basketball will not make you better unless you have never picked up a basketball before.
To anyone who says "custom games". Playing for 20 minutes to practice flashing a wall 4 times is a horrible training schedule. How would this improve, on any way, over a sandbox mode in which flash could be set on 0-CD and mastered in 20 minutes?
tl;dr By not supporting modes for training Rito is implicity supporting the idea that the horrible troll in your game has that he is at a professional level and you are the one holding him back. If they would create a training mode they would foster a community of improvement which would vastly outrank our current one.
PS I have faith, fixes for the new HUD make the game playable for me again. Rito has corrected in the past, they will do it again.