Friedrich Nietzsche is an example of someone who did not concur with Stoicism. Nietzsche, in his book Beyond Good & Evil, talks about how the Stoics created an unnecessary philosophy. He argues that if Stoicism is all about living in accordance with nature, and nature isn’t anything but indifference, injustice, cruelty, and hardships, then doesn’t living in accordance with nature simply mean living life if life is natural? What’s the use in creating a philosophy all about the already existing principles of life itself?
Nietzsche didn’t totally disagree with Stoicism even though some of his understanding may have been through misinterpretation. He sympathized with the story of Epictetus and the notion of a sort of individual Stoicism that involves personal goals and ideals, not the overall philosophy of Stoicism which includes a culture of people discussing their thoughts on the topic and not actually pursuing it. In his own words he seems to have respected Epictetus to some degree as being a slave who was able to bring himself up by his own significant resilience and not let the world take away from him the only thing which he ever truly owned; that which he could control.
Nietzsche admired Epictetus because he was a slave unlike the slaves of Christianity who put their hopes and beliefs in a single, mystical, glorious and powerful God. “Epictetus, on the other hand, neither hopes nor allows his best treasure to be given him—he possesses it already, holds it bravely in his hand, and defies the world to take it away from him. Christianity was devised for another class of ancient slaves, for those who had a weak will and weak reason—that is to say, for the majority of slaves.” Here, when Nietzsche mentions Epictetus’s “best treasure,” perhaps he is referring to a sense of purpose and individual meaning that he argues is provided artificially to Christians from the core of their religious dogma - God.
Another point of view as to why Stoicism isn’t great is that it can be emotionally repressive, which might lead to something negative happening. For instance, when something obstructive occurs that’s not a person's fault, it may feel natural to get angry, openly frustrated, and annoyed. But, with Stoicism a person doesn’t allow these emotions to get in the way of them continuing with the task at hand and completing it. Because that person didn’t have the emotional response that they tried to suppress, then the attitude of change won’t be as automatic and present. Perhaps as a side effect of this, the same negative thing might repeat itself because the proper emotional processes that motivate change didn’t manifest themselves or weren’t permitted to. This idea is the basis for some people’s disbelief in Stoicism.