For a new product/app, the onus is on the company creating it to explain why I would want/need their product. I'm not going to go around installing random things on my phone just to 'find out what it does'. I want at least some idea of what the app does before installing.
No compelling use-case? No download.
There are many good reasons to be a late adopter, safety is one. I don't think they should optimize their landing page for late adopters.
Judging from the site I thought Plague would be a new take on Reddit. Where Reddit asks if you like or dislike a Meme (we need a new word). Plague asks if you want to slow down or speed up its spread. This difference should mean different content is surfaced.
Late adopters will probably already know about the product before downloading it. It's the first adopters you need to provide the description for.