GEDCOM dialect differences are inevitable.
In the past, I’ve seen proposals for monolithic Import plugins that would supersede the built-in GEDCOM Import plug-in. So that it could support missing tags or commonly used custom tags. (But I have not seen those evolutions emerge between major releases.)
Or an alternative add-on Exporter plug-in such as GEDCOM Extensions. (Which has no corresponding Import add-on plug-in.)
But is is viable to build plug-ins that could extend the built-in Importer based on what dialect is identified in the header of the file?
So if the Importer found Ancestry or MyHeritage to be the exporting software, the importer could dynamically extend its dictionary to recognize that dialect and supersede the handling of standard tags that the exporting program mangles?
And do this as an add-on so that they could evolve?