An Honest Confession About Sandbox
So Riot recently put out a statement saying that they didn't want to create a sandbox mode since it would make new players feel like they have to grind it to get better.
Well, it's true.
When I first started over a year ago, I was way in over my head. Faced with learning the mechanics to a new game, I played mostly Co-op vs Ai games. I played about a hundred of them, and even then some after hitting Lv 30. I didn't feel I was adequate enough to play a real PVP game, so I just kept grinding until I felt I had enough AI experience to go play a PVP game.
Maybe a lot of you don't consider this, and just jumped into pvp without caring, but I didn't want to drag down my team by being the only scrub there.
But here's the thing. Even without Sandbox, I felt like I had to grind AI games. So it kinda' invalidates the argument. Even without a Sandbox mode, new players will always feel pressured to play about a hundred CO-OP vs AI games, because that's the next best thing. Actually, if anything they might feel that playing an AI game is better than sandbox, since it rewards you XP and IP for playing it, and a Sandbox Custom wouldn't.
So, here's my sincere opinion:
TL:DR - Riot there's already a mode new players feel pressured to grind until they're good, one that actually gives rewards. Offering your more experienced players a tool to go experiment and possibly find bugs for you to patch out should be encouraged. Maybe you should reconsider your judgement on this matter.