I commonly browse all by new, and I block users who crosspost any given article to more than one other community. To me it’s almost always a sign that they actually don’t care about the topic or contents, but instead their own post count and user recognition.
For me, you are. Imagine thematic communities in a tree-like chart: there’s the Entertainment community, there’s the Music community, and there are the communities by subgenres, music memes community, artists’ pains and struggles community. The narrow topic should belong to the farthest branch of this tree, IMO. The higher-level communities (wider themes) should only get posts that do not meet any of the lower-level (narrower themes). The narrow community should form as soon as the high-level one gets regular posts of enough quantity to form one (subjectively).
This stance would make sense if groups were in any way tree-structured.
They aren’t.
The two groups I mentioned above are (I think) on entirely different instances. (If they aren’t, they could be.) There’s no hierarchy.
You are right. I am, as always, idealizing.