Good Mornings should not look like a conventional deadlift. In a conventional deadlift your knees should go forward, equal to or often beyond your toes. That should not happen at all in a GM. In fact, a GM should look a lot like a... RDL.
I agree it is possible you might feel the RDL more in the hams, but to say a GM is a glute isolation exercise is not accurate. The erectors and hamstrings play a huge role in the exercise as well. Nor are RDL's a hamstring isolation exercise given the glutes, erectors, traps, and forearm flexors are all heavily involved.