Currently we have hard-coded a few extension pages that are not compatible with VE (FileImporter, Translate, and TwoColumnConflict). There should be a way for extensions to declare when VE can't be used.
Current hack:
// Not on pages which are outputs of the Translate extensions // TODO: Allow the Translate extension to do this itself mw.config.get( 'wgTranslatePageTranslation' ) !== 'translation' && // Not on the editor in the FileImporter dialog (T298345) // TODO: Allow the FileImporter extension to do this itself (T174180) !mw.config.get( 'wgFileImporterEditor' )