So, first of all, there are significantly fewer communities and users here on the Threadiverse. However, there is at least one other major factor, as your home instance isn't a huge one.

The way Lemmy and Mbin and PieFed work, any given home instance---you're on feddit.online---doesn't automatically download content from communities created on remote instances. They don't even know about remote instances.

It only starts downloading posts and comments and such once at least one user on your instance subscribes to that community.

Your All feed won't show everything on the Threadiverse. There's lots of stuff that your instance is oblivious to. It'll only show the posts from communities on instances that it's downloading posts from.

For a large instance like lemmy.world, this isn't a huge factor, but for smaller ones, it's a bigger issue.

https://lemmy.fediverse.observer/list

lemmy.world has 13,155 active users.

https://piefed.fediverse.observer/list

feddit.online, which is your home instance, has 164 active users. Probably not many people out searching for and subscribing to new communities!

There is a website that crawls all of the Threadiverse and builds up a list of communities on all instances: lemmyverse.net. They have a page that lets you search through and browse the list of communities:

https://lemmyverse.net/communities

Unfortunately, this page isn't made obvious to most new users. Oh, and note that the default setting on that page is to not show NSFW---pornographic---communities, if you're on the hunt for those, but you can flip that on with the checkbox in the upper left.

But if you go there, you can look through the list of all of the communities out there. If you find a community that you like, say, !photography@lemmy.world, you can click on it to copy the text [!photography@lemmy.world](/c/photography@lemmy.world), and then search for it using your home instance's search, and that'll let your home instance find out about the instance and community if it doesn't already and if you subscribe to it, it'll start downloading the content from that instance and show up in the All feed for other users on your home instance.

In general, I recommend that people try to build up a subscribed-to list of communities that they are interested in and then browse Subscribed rather than relying on All. All necessarily is only going to show some of the content out there. It can be a way to find new communities, but it's always going to miss content, and it's less-effective for that on smaller home instances.

EDIT: There are also two communities that it's helpful to be aware of if you're looking for new communities. You might want to subscribe to these:

• !newcommunities@lemmy.world: this has people post when they are creating a new community. The caveat is that all of the communities here are going to be empty when posted, and some may not take off.

• !communitypromo@lemmy.ca: This has people post stuff about communities (new or old) to help make them more visible.

In general, I think that lemmyverse.net is a better route than monitoring these communities---much easier to browse a full list of communities---but you might always also get some benefit there, and lemmyverse.net isn't "part" of the Threadiverse itself, just a convenient search engine/browser, whereas the above two communities are part of the Threadiverse.