While I agree with the basics of your reply taken from the Rosetta page, that the GEDCOM concept is old, Rosetta is a hub and spoke system of standardizing data transference across a shared system where the databases of said system are of different platforms, ex: DB2, SQL variants, Oracle, et al. It is a centralized means of incorporating various databases into one cohesive whole.
Rosetta is designed as a hub-and-spoke model where a common, open/extensible storage format forms the hub, and pluggable connectors to each supported application act as the spoke. Each application-specific plugin is tasked with handling the work necessary to Import and Export directly to the databases involved. My italics.
If Rosetta can get the pay for use sites, Ancestry, MyHeritage, FindMyPast, etc and the free sites or almost free, Geni, WIkiTree, Family Search, etc, to permit a plug-in application to have direct and unencumbered access to their proprietary databases, good luck to them.
A GEDCOM file is exactly that, a file. It is not a separate database. It is a means of transferring data from one site/program to another in a standardized format. Is it perfect, no. Does it work, mostly yes. Does a new standard need to be created as the computing world progresses, yes. Is the Rosetta standard it, not at this time. A nice dream, but given the legal constraints of the ownership of the various genealogy databases in this day and age, no.
To paraphrase Lincoln, you can't be all things to all people at all times.