It is now well known that serotonin uptake cannot explain the effect of SSRIs and that we don't actually know how they work- but that doesn't mean they don't work. Most drugs have many effects (we call some of them side effects) and this isn't the first drug where we thought we knew how it worked and ended up being wrong.

Some have found flaws with Kirsh's study and there is still an ongoing debate about effectiveness. [1] I am not a fan of prescribing so many people a drug that we don't know how it even works for what is often just a small improvement, but I don't think its accurate to say they are useless.

[1] https://academic.oup.com/ijnp/article/14/3/405/906146#156821...