A drawback of the core plug-in is it's high complexity. While the microkernel provides just the bare some bare functions and structures, the core plug-in adds a whole bunch of components at once. It can be challenging to decompose the core architecture and understand the connections between the components. This documentation could only cover the most important parts. This gives a developer the choice of building a whole new application on the microkernel or building the application on the core plug-in, including all modules and UI tiddlers.