The other day I asked for an analysis or at least an UML diagram since we are having quite some troubles and my boss looked disgusted at me for asking such a question. I’m not a professional backend developer, so I don’t know how it works professionally
This is such a broad question. It’s normal and not normal to do so, it’s also normal not to do so.
If it turns out / becomes evident you need a diagram now now’s the time to create one. You may push quality even without seeing the value in it. In some places or with some people it may be unwanted.