Earlier quoted context omitted.
If "All [MDMA] does is artificially increase serotonin.... just like prozac" then Prozac and MDMA would have the same effect. But they have radically different effects, so they must do at least something differently, despite sharing some similarities.
Yes, it works more quickly. That’s the only difference. And it is more like the SNRIs, like cymbalta with some effect or encouraging the release of catecholamines. But the effect is the same, more neurotransmitters in the synaptic cleft. People abuse Prozac as well if that given you a clue on their similarities. https://pubmed.ncbi.nlm.nih.gov/8093133/ https://ajp.psychiatryonline.org/doi/abs/10.1176/ajp.150.12....
It's like saying that a helicopter and a blender are the same device because they both have spinning blades. These two substances are completely different in just about every way that they affect people, aside from producing a mood boost (which is an effect also caused by things like morphine, cocaine, a few different psychedelics, alcohol, caffeine, nitrous oxide, and many many more substances which don't act via serotonin).
One of the main theories on the action of MDMA involves the sudden serotonin release inhibiting the amygdala and thus reducing fear response. Prozac certainly does not do this. MDMA's effects are not even all shared with other serotonin releasers such as fenfluoramine or MDAI. And Prozac's effects differ somewhat from other SSRIs too.
The neurotransmitters and receptors in the brain are not a set of dials where you can ratchet one and always expect a given psychological effect independent of the other receptors, or even independent of the way it's ratcheted, or even the timing of it. Also the effect of these drugs is highly dependent on context too. Believe it or not, MDMA can sometimes produce dysphoria and or unpleasant/unhappy mental state. It is uncommon, but I have seen it happen.
Sorry for the rant, it's just this type of oversimplification really strikes a nerve with me.