Riot, you severely undervalue 2-way mobility

It seems like champions with dashes or heavy speed buffs that work when approaching and fleeing an enemy are in a league of their own and other champions are essentially irrelevant. No reasonable advantage in any other stat makes up for one champion being able to always choose when the fight starts and when it ends. Not only do champions with 2-way mobility get to initiate when they want to, but they can just leave the fight if they made a bad call and start to lose. I'm pretty much only playing those champions now and it is a little sad because there are other champions I'd like to explore, but they all seem worthless. Does anyone have a trick to making non-mobile champions work against champions that can without fail kill you when they are ahead and escape when they are behind?