When building large-scale applications with React, it's important to be aware of the downsides of using hooks, as they can potentially lead to complex and difficult-to-debug code.

One downside of hooks is that they can make it harder to understand the flow of a component. Because hooks are used to manage state and side effects within a component, it can be difficult to trace how data is flowing through the component and how state changes are affecting the component's behavior.

Another downside of hooks is that they can make it harder to test a component. Because hooks are used to manage state and side effects within a component, it can be difficult to isolate a component for testing and to ensure that the component is functioning as expected.

Additionally, hooks can lead to increased complexity in the component hierarchy. As the component becomes more complex, it can be difficult to understand the component's dependencies and how they affect its behavior.

Hooks also can lead to a lot of repetitive code, especially if you have a lot of shared logic that needs to be used across different components. This can make it difficult to manage and maintain the codebase.

Lastly, hooks can make it difficult to follow the best practices for accessibility. Developers may inadvertently introduce accessibility issues when using hooks, such as not properly handling focus or not providing appropriate labels for form elements.

It's important to keep these downsides in mind when building large-scale applications with React and hooks. By being aware of these potential issues, developers can take steps to mitigate them and ensure that their application is as stable and maintainable as possible.