Microservices with a share datasource are just a Service Oriented Architecture, circa 2005. You might have a variety of middle tier services, deployed in their own boxes, or at the very least Java service containers, but ultimately talking to some giant Oracle DB behind it. Microservices that share a database are not deployed into a container running JBoss, and instead use something more language-agnostic, but it's ultimately the same thing. All you have to do is quote the many criticisms of that era, when any significant DB change was either impossible, or required dozens of teams to change things in unison.

The best imagery I know for this picture is a two-headed ogre. It might have multiple heads, but one digestive system. Doesn't matter which head is doing the eating, ultimately you have the same shit. I've head semi famous people talk about this in conferences, but few articles.