All true Japanese maples are variants of Acer palmatum. You have purchased a great tree but may have managed it incorrectly - hopefully not beyond recovery. Japanese Maples come in several leaf colors and forms. The easiest trees to propagate are the green-leaved varieties. So nurseries grow green root stock and graft red-leaved stock off that root.
You have allowed the green stock tree (which will sucker from below the graft) to become the dominant foliage. Your photo shows a classic example of this.
Manage only the foliage above the graft line (if you have any left) and remove all green sprouts below. The tree's symmetry may be upset for a while. Japanese maple is a slow grower and you must give it time to develop its natural form. Heavy pruning is not necessary nor recommended.
Japanese Maple With Green and Red Leaves - Photo by Larry