The problem I have is to rebuild a 10-year-old web application with hundreds of features, heavy customization, used mainly on tablet/smartphone

The most important factors for me are feature switching on/off, modularity, speed of interaction on mobile devices, modern GUI interaction (ajax, native-like, etc).

Somebody proposed Liferay as a framework. I really would like to understand if Liferay (a CMS based on portlet specification) makes sense. My idea is based on a Spring Boot backend + a JS framework