This doesn't make sense - the apps that aren't in the list of the top 300,000 downloaded apps may not get many downloads as far as we know, but without further information, how can you arbitrarily declare that as the threshold for "zombieness"?
Realistically though, it is really hard to get some attention in the App Store nowadays, and Apple really should build some mechanism into the store to combat this.
I believe it - it'd be nice if apps get moved to a separate list if they don't receive downloads after a (long) period of time so that newer apps have a chance to cut through the noise and get noticed easier.
Cut through what noise? Moved from what list? If you're not a ranked app, you don't seem to be in a list at all, as far as users are concerned.
It seems if you're not at least in the top 100 in your narrowest category, you are equally (in)visible whether you're ranked 1000 or 100000, thus only get found by a direct link from outside the app store (zero noise) or a quite explicit search (specific intent). For these, the number of other invisible apps seems irrelevant.
Put another way, if you want to be on the top lists, you're going to need promotion. Get noticed to get noticed.
Realistically though, it is really hard to get some attention in the App Store nowadays, and Apple really should build some mechanism into the store to combat this.