It's not even a pay wall so much as a play wall. You noodle along fine at low levels and all of a sudden you run into people with one or more units rocking twice the attack or hp and all your carefully considered tactics dissolve in a puff of smoke. It's a bit like playing chess except after a few game one side starts with rooks instead of pawns, and being on either end of that imbalance is boring. I'm not talking about ranked fights either, just regular battles suffer from this.