Most communities are not the sole community related to their topic, there are really often other communities on the same, or similar topics.
An example: there are a tonne of art related comunities, but only a small handful of them have links to other related communities.
It would be great if there was more of a culture of propping up semi-related communities. This would be particularly useful for helping more niche communities get rolling.
If there are clear distinctions between them, this is a good thing IMO. If I sign up for a community, I want to see content that’s on topic. If I see too much unrelated stuff, I’ll leave. If I want to see both types of topic, I can just join both.