Is there a way to navigate lemmy that will show me everything?
Sort of, on the liftoff mobile app, you can. There are probably other apps as well. You have to sign up for all of those instances that cover what you want to see though, then input them into the app. The app can get fussy when you do this, but it lets you see everything and you can easily switch to instance you want to post from.
If you mean every instance, then not that I’m aware of. Someone might know of a developer that lets you at least see every instance. I doubt there is one that you can comment and post on every one.