For example, imagine Digital Ocean using MongoDB to store server configurations. AGPL would force them to open-source their whole infrastructure. All of it. Or pay to get a different license.

I don't have a moral argument to make here -- just making sure people realize the actual trade-offs. AGPL is theoretically for a world where closed source software is simply not allowed to co-exist with opensource, even if you don't distribute it, but simply run it / host it / use it. But that world doesn't exist, so it does the opposite: it is actually used to make sure some of your users have to pay. It enables a business model.