Debian is a large, complex operating system, and a huge open source project. It’s thirty years old now. To many people, some of its aspects are weird. Most such things have a good reason, but it can be hard to find out what it is. This is an attempt to answer some such questions, without being a detailed history of the project.
Vanilla just means they have no ideas about changing anything. It may be good to not duplicate effords or annoy Desktop developers. But its not really something crazy great