Obsolescence of theming and overlay techniques
Using deep ng-host is no longer effective for customizing components like the Prime carousel or Angular Material elements. This approach, once widespread, is now unsuitable for the evolution of front-end frameworks.

New approaches for theme customization
To replace overlay techniques, new tools and methodologies have emerged. The use of SCSS stylesheets now allows for finer and more robust theme customization. This approach offers better maintainability and more seamless integration with modern component libraries.

Importance of modularity and extensibility
Beyond simple theming issues, web application design must now take into account the extensibility and modularity of the technical solutions used. Developers must adapt to the rapid changes in front-end frameworks and libraries, favoring flexible architectures and agile development practices.