You're oversimplifying the picture. The criticism isn't that it's not evidence-based, it's that the approach of the GIDS is out of step with the cautious exploratory psychoanalytic approach that characterises the rest of the work done by the Tavistock and Portman. What David Bell says, amongst other reported criticisms, was that there isn't sufficient time and space given to exploring individual and family history and context and trauma. I'm sure that's the case. There is less and less time given to exploring individual and family histories in clinics everywhere as all services have huge waiting lists and have become increasingly medical with a focus on through-put. The people making criticisms are making them from the point of view of the need to get to know the patient/client first and foremost, over time, that's the kind of evidence they, and I, believe is needed.
David Bell and Marcus Evans are very senior clinicians. I know that because this is my field. I have their books, I read their papers, and if I saw they were speaking at a conference, I would try to attend. I'm very interested and take very seriously what they say. But the media is simplifying a complex political and clinical picture; as they can't even report correctly which service these two clinicians work for, I don't trust them with much else. They don't work for GIDS, they are senior staff in the Tavistock Clinic.