blind pick is not a proper learning environment. neither is ranked.

why are you removing the only tool players have to practice in league of legends?

there is more to the game than what goes on after the game loads.

there are things that happen in champ select that you also need to know about and how to react to them.

i used to only play blind pick and when i started playing draft, i felt completely overwhelmed, luckily for others i wasnt playing ranked, i was playing draft, about a year into playing only draft did i feel i had a good handle on my lane, good enough to hop into ranked for 20 games and land myself in bronze 5, but thats besides the point. the point is, blind pick is a terrible environment to learn. there is no guarantee of an even half way decent champ select, there is no guarantee you wont land with double jungle or pantheon j4 kill lane bot. its only a step above bots in terms of practice potential.

ranked is too serious. people dont feel like dealing with you learning in ranked. in ranked you need to know wtf you are doing already.

blind pick does not give you any learning opportunities. most of the time in blind pick you will be matched up against a champion that is surely to be banned in draft, and the remained of the time you get put up against terribly out of meta champions that learning the matchup does not help with anything at all.

now you did say there is a sandbox mode coming, which is fine for practicing some things, like a combo, or last hitting, or whatever, but for practicing overall game strategy nothing beats playing against plausible scenarios. and blind pick does not provide you with this.