One of the major developments of modern CBT has been the 'third wave' approach, such as MBCT (Mindfulness-Based Cognitive Therapy), ACT (Acceptance and Commitment Therapy and CFT (Compassion-Focused Therapy). Has REBT been left behind, dating its origins way back to the early 1960s, even before the 'cognitive' revolution? In my opinion, REBT, was not only ahead of his time then, but is still in key respects ahead even of the third wave approaches, thanks to the vision of its inventor the late Albert Ellis.
One of the important influences in the development of third wave CBT was the introduction of aspects of Buddhism, particularly mindfulness meditation and the change that this can bring about in relating to emotional distress such as anxiety and depression, and admittedly this aspect of Buddhism was not specifically introduced by Ellis - but can be and is being so introduced by some REBT innovators.
But another key aspect that Ellis did introduce explicitly which the third wave do not, and that is remarkably similar to Buddhist 'insight', is the idea that our 'Self' is unrateable, that our 'Self' has no essence, but that we irrationally believe we each have such a Self which is some kind of fixed entity that we must judge as worthwhile or worthless, good or bad, flawed or flawless, depending upon some social criterion that we must have, such as being liked or doing well at some task, and if we don't have, we are judged as no good at all. The Buddhist insight that there is no such 'thing' as the self is more explicit, but Ellis' idea is no different, and the discovery that there is no such fixed self is as liberating for successful REBT clients as it is for people who follow the Buddhist path. The REBT method is one way to achieve happiness and overcome emotional disturbance, mindfulness meditation where 'Insight' is the goal is another, but there is no reason at all why the two approaches cannot be combined to powerful effect.