The generic target builds all packages included in T2 that are enabled by default. This generally is everything but stuff that is known to be broken or conflicts with other system compoentes, such as alternative printing systems, C libraries, init and login systems, etc.
The generic target is meant to be for people requiring a vanilla GNU/Linux flavour and used for testing by T2 developers.
As soon as people do not like to have such a big package pool and focus on a specific area of desktop, server or embedded computing they usuall use another, less generic T2 target.