As per this post, it seems Lemmy World is having federation issues. I've had some of my posts and comments get suspiciously low response, so I've looked into it and it turns out that many of them aren't showing on other instances.
Here's an example: my Payday 3 post is only visible on Lemmy.world:
Meanwhile, in other instances, it doesn't show up at all:
It's not clear if this issue is exclusive to this instance but I thought I'd give people a heads up. I reposted and now it showed up in other instances. If you feel like you're getting no response from other communities, check on another instance if your content is visible, otherwise repost it.
It's almost certainly technical issues relating to scalability. The user I mentioned above has created a community for tracking several performance issues that are likely impacting the platform now that user and post counts have increased exponentially.