system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If SSRIs all do the same thing (prevent the reuptake of serotonin), why are there different SSRI meds that have varying levels of usefulness?
gpt
They don't all do the same thing, really.

SSRIs interact at a LOT of receptors, and with different affinities.  They have different pharmacokinetics from drug to drug.

All SSRIs "do the same thing" the same way that all hot sauces "make stuff hot."  That doesn't mean every hot sauce is the same, have the same taste, or can be completely interchangeable.