Any game mode where i can try new champions without getting flamed and detroyed?

Usually in the laning phase when i use my mains i make people quit and get flamed from the enemy team but once in a while i want to play something different, thing is everytime i try i always end up vs the kid with 150k exp in normal playing like they are in challenger promos and is miserable. I get destroyed with a champion i never tried, flamed from my team and reported. There should be a game mode where you are not allowed to use champions with over 10k exp or something cause the whole experince makes me not even want to try anything new anymore
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