For a philosophy that is founded on usefulness I don't see much of a disadvantage. But, I'd love know more about it.
Wikipedia describes utilitarianism as
Utilitarianism is a family of consequentialist ethical theories that promotes actions that maximize happiness and well-being for the majority of a population.
The article lists ten criticisms of utilitarianism which might be viewed as disadvantages. Here are two of them.
- Does focusing on utility ignore justice? That is, would utilitarianism "be prepared to punish an innocent person for the greater good"?
This issue is also raised by G. E. M. Anscombe more generally in Modern Moral Philosophy. At the end of her paper she claims that her complaint is that such theories permit one "to procure the judicial condemnation of the innocent".
Some argue that it is impossible to do the calculation that utilitarianism requires because consequences are inherently unknowable.
Anscombe, G. E. M. (1958). Modern moral philosophy. Philosophy, 33(124), 1-19.
Wikipedia contributors. (2019, May 19). Utilitarianism. In Wikipedia, The Free Encyclopedia. Retrieved 12:33, May 22, 2019, from https://en.wikipedia.org/w/index.php?title=Utilitarianism&oldid=897848977