It is true that R. G. A. Buxton, among others, disdains this approach, see esp. pp. 25-27 of "Euripides' Alkestis: five aspects of an interpretation," Papers given at a Colloquium on Greek Drama in honour of R. P. Winnington-Ingram, Lyn Rodley, ed., 17-31. Although I agree with Buxton that Admetus is presented with sympathy rather than censure, I do believe that his place in the criticism is justified.