Wish we could make slice catch on. Not only for the reason you mentioned, but it also implies that what you are looking at is a part of a whole. So communities are a slice of lemmy.
The term "community" more or less settled, but if you are looking for something more distinct, there is an idea to call ourselves lemmings and the communities /c/liffs that we jump on. Alternatively we could call ourselves lemmons and the communities /c/itrusses.
They already have a name, straight from the documentation: "communities". You can call something a "community" and everyone knows exactly what you mean. Call it something contrived like a "sublemmy" and you have to explain it every time.
I disagree, I feel the opposite. If I google, say, "x hometown community", I'm going to get literally everything about my home town. "x hometown sublemmy's(or whatever)" on the otherhand, would be fine tuned to show me lemmy communities about my hometown.
It could be something unbranded, like “communities,” as long as it was consistently used by all. But to have some call it topics, some call it communities, and some call it channels just gets confusing. I’m not even going to comment on “magazines.”
Calling the communities "sublemmies" for example, would mean that people on kbin have to call it like that too. And afaik they are called in a general way for the fediverse, just like how mastodon changed toot to post.
Does this make the platforms less unique?
Yes, absolutely, but I don't think there is a fix for it.