If you go to Posts/All, you will see all the local communities plus all the communities subscribed to by the instance. I don’t foresee every instance mirroring the content of every community from every other instance - storage and bandwidth would go through the roof.

Communities that haven’t been subscribed to yet on an instance take a few minutes to show up after you search for them. This is something the need to fix: the delay is fine, but the need to provide useful user feedback, “connecting to community, check back in a few minutes”

Try this: https://browse.feddit.de/

I’ll agree that fetching a new community is much more awkward than it should be.