Holism is a philosophical idea where every idea in the natural realm is being viewed as a whole and not as collected parts. It has many advantages like you can view the clear picture of the things. Since you are able to see the scenario, you can prose direct, appropriate and instant solution/s upon it. Ideas are direct with less complexities and struggles. It poses clear yes and no questions.
If we look on its disadvantages, we should think about reductionism or atomism. It is the complete opposite of holism where anything can be viewed from reducing the parts to understand the whole. Holism tends to simplify whole things that cannot really be simplified such as diseases and diagnosis. Holism prevents further researches that can help in understanding the problem. It is less scientific than reductionism because it is not uncovering complexities. And lastly, holism is becoming hypothetical in the fact that it sums up or concludes a whole thing without weighing the effect of its parts.