for moderate to severe depression, the kind most posters are talking about, they're consistently better than placebo. It is true that placebo is often effective too. But most people I talk to would rather have that extra chance of getting better.
If “placebo-resistant depression” and “treatment-resistant depression” were synonyms, we would expect that excluding treatment-resistant depression from your study would result in the studying showing precisely no difference between treatment and placebo. The fact that the meta-analysis shows any difference at all suggests that “treatment-resistant depression” might be a meaningful category.
I wouldn't dismiss a meta-analysis out of hand, but at the same time...isn't there a strong pressure to publish an effect above placebo? They rated 73% of the studies as having a moderate risk of bias, and certainty of the evidence ranged from moderate to very low.
https://www.ncbi.nlm.nih.gov/pubmed/29477251
for moderate to severe depression, the kind most posters are talking about, they're consistently better than placebo. It is true that placebo is often effective too. But most people I talk to would rather have that extra chance of getting better.