How about WordPress?
Specifically about WordPress, I have started to use this tool and its ecosystem professionally more than 10 years ago, developing plugins, themes, customizing solutions and build integrations.
I am a web development enthusiast also being an active member in the local WordPress community, contributing with lectures and sharing knowledge in groups and other professionals and companies as a consultant.
A framework I can call my own
A few years ago I noticed the recurrence of projects in which a web application was very dependent on WordPress resources to share content, users and functionalities and the same happens a lot in the opposite way.
Based on WrapBootstrap and the WordPress documentation, I have created a theme that, when installed, provides a quick and safe way to create an application following known MVC standards and that in a few minutes is already available to be accessed.
From there, efforts can be concentrated on developing the application to meet business requirements and rules. This integration allows the developed application to take advantage of the thousands of existing solutions in the WordPress plugin directory.
A number of clients today use applications that are fully integrated with WordPress, such as BNI Brasil, FireEventos, Agile Marcas e Patentes, PCVN and some others.