It is. Both GE and P&W newest generation of engines realized on the order of 20% efficiency gains over their previous products. They both cost in the billions / 10's of billions in r&d, which may sound doable, but realize that they were both starting off with organizations (engineers, facilities, decades of experience, etc.) built to do that. China has thrown 10's of billions and 10's of thousands of people at this problem and still hasn't cracked it after 10ish years.