Old URF was better because of build experimentation.

When you can play the same champ multiple times, you can try to see what works for you. Now you are stuck with whatever you come up with on the spot that might fit the situation. While also getting to grips with a champ you never play with cooldowns that feel totally new. By the time you have things sorted, the enemy OP champ they "lucked" (ARAM ACCOUNTS) into is fed and it doesn't even matter any more. And if you get an OP champ, finely tuning the buildpath doesn't matter either. Because OP. At least when everyone is OP choices matter.