As someone who has taken SSRIs they usually do have effects. You can take them as a healthy person and they also have usually effects.

There is more diversity to people and their thoughts than your simple philosophy suggests; people may suffer from mental illnesses for no apparent reason, like how people may suffer from poor health in the same environment as a healthy person. And with antidepressants on a person with a condition stemming from a poor lifestyle, the effects can be what makes the difference that helps them transition to a more sustainable lifestyle.

Ignorant, grandiose claims like these really don't help people suffering from mental illnesses.