'Ant-Man and the Wasp: Quantumania's mid-credits scene, explained

Sure, Ant-Man and the Wasp: Quantumania might have been a lackluster mess of poor CGI and an incredibly questionable plot, but its mid-credit scene tells us what's happening next in the Marvel Cinematic Universe. 

After accidentally getting warped into the quantum realm, Scott Lang aka Ant-Man (Paul Rudd) and co. face off...