Symfony 4 bundles working
the logic for creating bundle doesn't change since Symofony 2.x. But now bundles are just packages, use for reusable features.If you want to develop your own bundle just follow this post Symfony2 - creating own vendor bundle - project and git strategySince Symfony Generate Bundle isn't supported anymore in 4.x you have to follow this other post: Best Practices for Reusable Bundles
The SensioGeneratorBundle has been superseded by the Symfony Maker Bundle – see https://symfony.com/blog/introducing-the-symfony-maker-bundle for more information.
Fabien Potencier said in the Symfony 4 best practices blog post "Bundle-less applications is just one of the best practices changes for Symfony 4".
You must not generate new bundles, you can use default "App" bundle for your whole project.
You can look at this url for blog post about subjectSymfony 4: Monolith vs Micro