You are right in that, realistically, they are a poor choice for modern aircraft. Their agility advantages do not outweigh the structural and stealth disadvantages, particularly because modern combat is focused on the missile.
They offer better maneuverability at all speeds, but their advantages are most pronounced at high angles of attack and transonic speeds - areas where more conventional wings suffer from very poor airflow. At supersonic speeds the greater potential of forward wings are wasted because conventional wings offer enough maneuverability without as many structural concerns.
I'm trying to say that without consideration for stealth (UFOs use gravitic detection), and with much better materials (80 years of materials science, plus the usage of alien materials), forward-swept wings become a viable alternative - especially considering that the Dragon is a high-altitude, high-performance dogfighter replacing the Stiletto.