Quarto is a far bigger platform than R markdown. But, this is limited to only rendering markdown or its flavours with R or the like code sequences only.
Asciidoc is simpler has only one flavour with distinct features for writings very good books, articles and what not?
Therefore, I request its developer's to incorporate rendering facilities for Asciidoc documents to be written in Asciidoc quarto.
Wishing all the best hopefully,
Dr. A.K Singhe