For what is worth, the fact that any treatment has roughly the same effects (with some being slightly more or less effective in some subgroups in smallish samples) shows that the effects of all those treatments are likely placebo, or at minimum that there is nothing special about meditation (e.g. you can get the same benefit from talking to someone/listen to an audiobook or whatever).
Regarding the subgroup finding: as far as I know, the study was not designed or powered to rigorously measure the impact of the interventions on this subgroup. If they did another good study looking just at this subgroup and the results were positive, that's a different thing. The first thing investigators do when a study fails the primary endpoint is mine for subsets of the data that show a positive result. That doesn't make the result meaningless, but should invite skepticism
Reproducibility is a huge problem in scientific research. These are not determinate systems, and a huge number of things can bias a result, intentionally or otherwise. Scientific publications, even in good journals, need to be viewed with an appropriate amount of skepticism
According to NICE, one of the leading agencies on cost effectiveness and clinical guidelines, MBCT is only recommended for prevention of relapse in patients who have had three or more episodes of depression. CBT and augmenting antidepressants work just as well. Funny thing about depression studies is most interventions, pill or psychotherapy (or even placebo sometimes) tend to have similar levels of effect
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3964149/
The study literally says: "MBCT provided significant protection against relapse for participants with increased vulnerability due to history of childhood trauma, but showed no significant advantage in comparison to an active control treatment and usual care over the whole group of patients with recurrent depression."
Which means: in some cases MBCT is SIGNIFICANTLY BETTER than the compared treatments and overall it is AS GOOD AS the compared treatments (i.e. cognitive psychological education (CPE) and treatment as usual (TAU)).
Now, looking back at your post, you said "failed to show a therapeutic benefit" which is strange, because the mentioned study shows that the therapeutic benefit is about the same and sometimes it is even better compared to CPE and TAU. So why would you say that MBCT does not show therapeutic benefit if it has the same results as the other (best?) known treatment methods?
PS: I would really like to turn your biased question around: Do you know of any treatment method which is better than MBCT?