Back with newsgroups the general rule was to go from general to specific. You start with a general discussion group and when discussions about video games get annoying you create a games group. If then there are too many Baldur’s Gate discussions you create BG. If they are dominated by Baldur’s Gate 3 you create a Baldur’s Gate 3 group. If everyone is fawning over Withers you create a Withers group which of course will be flooded with discussion about the Withers’ tits mod, which shall get its own group.
Meaning you should create a group when demand is there and not the other way around.
I don’t think “hobbies” makes sense as a generalist community. No one is interested in “hobbies” as a general concept, they’re interested in their own specific hobby. Trying to consolidate completely unrelated hobbies into one space in the hopes that more people will subscribe won’t work if those people have no common ground to discuss together in that space.
I think something you’re missing is that “we create communities as needed” has an inverse as well. “We delete communities as needed”. Sometimes you create the general topic and it’s so general that all of the niches overtake it. When that happens and the general just isn’t needed, you prune it. No community has to exist forever and sometimes it’s only purpose will be as a reference point to others. And sometimes even that isn’t needed anymore and it vanishes too.
It’s a constantly changing, dynamic system. The point is that it should cater to what’s needed/being used at the moment.
At this moment, there are at least a few manual hobbies that could coexist on the same community
They don’t have to be as interested in the other ones as their own niche, but at least they can share space and activity.
You could potentially have an “outdoor hobbies” with fishing, camping, animal trapping etc.
You kind of already see this when all of those hobbies can post to !imadethis@lemm.ee