Does Meta And Champion Balance Really Matter Much?

Sure. In like Masters and Challenger i could understand a lower AD on a champ being exploited and costing you the game but what about Diamond? I get so much crap for playing Evelynn and when i ask for help on the forums people give the "Helpful" tip to give up and play any other champ. Is Evelynn really that bad? I don't even play ranked but i reckon if i was actually good at the game i could push Evelynn to challenger using her unique playstyle. Sure, there would be better choices but i doubt it's impossible. Does the meta and the ever shifting viability of champs matter that much before Diamond?