Generic views are views that perform a certain pre-defined action, like creating, editing or deleting objects, or simply showing a template.
Generic views have to be distinguished from functional views, which are always hand-written to perform the required tasks. In a nutshell, it can be said that generic views need to be configured, while functional views need to be programmed.
Generic views may save a lot of time, especially when you have many standardized tasks to perform.
These examples show that generic views generally make standardized tasks much simpler. Instead of programming everything from scratch, you configure what other people have already programmed for you. This makes sense in many situations, as it allows you concentrate more on the design of your projects rather than the processes in the background.
So, should you always use them? No. They only make sense as long as your tasks are fairly standardizes (loading, editig, deleting objects) and the more repetitive your tasks are. Using one specific generic view only once and then override all its methods to perform very speficic tasks may not make sense. You may be better off with a functional view here.
However, if you have plenty of views that require this functionality or if your tasks match excatly the defined tasks of a specific generic view, then generic views are exactly what you need in order to make your life simpler.