Pointless

Right now this plugin is totally without a need – Gutenberg is only available as a plugin and that can be simply removed if you don’t like it.

Once Gutenberg is standard within Core, the likelihood is that switching back to the old editor will require a different solution – from what I can tell this plugin simply uses older code for post editing (which isn’t going to be an ideal solution with regard to security updates, etc). Matt Mullenweg has already stated that a plugin to switch off Gutenberg will be made available in due course and I would recommend anyone to use that instead. But, right now, like a pencil with no lead, this plugin is pointless.