I entirely agree that we could've cared better for the leading 16 bit space. But protocol-wise adding a second component (images) to the concept of textual strings would've been a terrible choice.

The grande crime was that we squandered the space we were given by placing emojis outside the UTF-8 specification, where we already had a whooping 1.1 million code points at our disposal.

> The grande crime was that we squandered the space we were given by placing emojis outside the UTF-8 specification

I'm not sure what you mean by this. The UTF-8 specification was written long before emoji were included in Unicode, and generally has no bearing on what characters it's used to encode.