I think it basically died for general consumers because of the Canonical-only licensed software lock in, and consequent limited software support.

Snaps are hard coded to only be able to get snaps from the official Canonical-licensed store URL. Especially on Ubuntu Core, where everything can only be a snap. Even the commercial licensed version for embedding in products requires private companies to use a private space on the Canonical Snap store to distribute thier custom/proprietary software. Absolutely no one is willing to let Canonical become the Apple Store of thier devices, especially given thier even shittier track record.