The quick answer is yes! But there are many common ways to make Christmas ornaments. Many toys use injection molding so that they can be mass produced and the same thing would apply to Christmas ornaments.
The most common materials for modern Christmas ornaments are glass, metal, plastic and wood. Ornaments come in a nearly infinite number of shapes, but here are some of the most common ones: Ball ornaments. The popular standard Christmas ball ornament can be made of metal, glass or plastic. In some cases injection molding is used, however, there are plenty of the more expensive unique glass blown ornaments that require a blown glass technique. Regardless of how they are made, the art of making Christmas ornaments have been around for centuries. See: https://www.history.com/topics/christmas/history-of-christmas-trees