Although depression is not well understood, there are some theories/interpretations of the data. One of which is the differences of mechanism behind 5-HT_1A and 5-HT_2A:
SSRIs are (stronger) antagonists for 5-HT_1A which is theorised to increase "passive coping". Psychadelics are (stronger) antagonists for 5-HT_2A which is theorised to increase "active coping".
The original paper that proposes this is "Serotonin and brain function: a tale of two receptors" by Harris and Nutt, hopefully my simplification has been accurate enough.
This is quite interesting as it mirrors not only what I've experienced but also the conversations I've had with other. The following is obviously the anecdotal opinion of a single person. Firstly neither SSRIs or Psychadelics by themselves "fix the problems with the world" - if being in debt living paycheck to paycheck or having a bad relationship is a contributing factor then taking medication doesn't magically make that go away.
Whilst on SSRIs, although there was an objective decrease in symptoms subjectively it it became increasingly difficult to continue the course of medication. This is not uncommon, as can be seen in "Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis" by Andrea Cipriani et al. In contrast psychadelics and the "mania", flexible thinking, decreased pessimism they induced combined with the subjective contrast was extremely insightful - "oh yeah, I can be happy". Although objectively my actions did not change much, subjectivly they were no longer "shameful", I didn't need to ruminate and accepted them.
But it should be said, taking psychadelics when not in a good mental state is incredibly dangerous, especially if it is the first time. This is mirrored in this review of a review (https://astralcodexten.substack.com/p/on-cerebralab-on-nuttc...). To quote the original review:
> I found it curious that people who take psychedelics for introspection usually end up as religious cranks or burnouts. While people that take psychedelics because "they are fun" don't seem to experience many negative side effects. Under this framework, it makes perfect sense, activate highly conceptual functions in the cortex and tell them to solve an intrinsic and emotional, you'll end up with some very weird conceptual scaffolding.