Correct. No one can use something that they don’t know about.
Right now Lemmy is really best for centralized populated instances that have a similar experience to being on Reddit. Federation is a bonus. There are a lot of problems with trying to access content on other instances. Weirdly, the name of the sub is not shown in the URL for posts. Someone might be able to create an alternate web client, but that adds another layer of complexity for people who just want to run the site.
The main problem with federation is that there’s no “site” that people know to go to.