The structured discussions feature provided by Flow is not and has never been "dead".
Some communities are using it on a regular basis as they appreciate it, and the developers have kept on with maintenance tasks and bug fixes. This year, we will make some changes to structured discussions based on feedback, as we documented in the annual plan. The editor-facing changes will be announced to the affected communities soon.
The structured discussions feature is not and will not be deployed to editing communities that don't want it. As it's an editor-focused feature, unlike MediaViewer, it has to work well for a majority of editing community members to be successful. That shouldn't prevent some communities from using it just because other communities don't want to.
It is wrong to say that all wiki pages are alike, and that structured discussions are the only departure from this. Each "structured data storage" system differs from other wiki pages. Most simply, file pages are radically different (you have to 'upload' to change them). In Wikibase (used for Wikidata with other future uses being worked on by several teams), "pages" have a completely different storage/editing mechanism. Wikisource also uses a very different editing system for side-by-side correction of OCR'ed texts, which is more appropriate for that set of needs. In the same way, a structured discussion system has unique needs. Getting it implemented will have a known list of benefits, that communities have been asking for over many years, and that are impossible to implement in a non-structured plain wiki page.