How easily you can manage users and connect users to an e-mail newsletter and billing profiles right in the backend.

Joomla have a lot of flexibility with its powerful development framework and smart to use cms system. You can also build easy apps ( extensions ) with many Joomlas CCKs example https://www.seblod.com/ or free Joomla component builder https://www.joomlacomponentbuilder.com/ Its also easy to have design templates/frameworks for rapid website building example https://www.joomshaper.com/page-builder and where you have a lot of many great large/small extensions example https://www.regularlabs.com/extensions/advancedmodulemanager/tutorial to modify/visulize your system to whatever you like. Joomla is also owned by its community and is 100% free with no encryptation whatsever..

It's simply the best tool for complex websites where you need heavy customization. It allows you to manage everything without the need of installing plugins like Wordpress. I've been using this since version 1, so I belive I have more than 20 years of experience using this daily and I've seen how it has evolved. It is very easy to install and implement. When you find developers that really care and really improve their components, you can rely on them. But you have to find them first!