My company doesn't have the latest version of Office, and the version dates we do have can vary by a few years, so I just save everything I touch in a 15 year old format, because the new format provides nothing I need for 99.9% of documents, and the remaining 0.1% can be pdf. I use LibreOffice. Others use Word 2016 or 2012, and none of it particularly matters.
For governments, the things LibreOffice complains about with OOXML ought to be security concerns. If you can't know how to duplicate what's correct, then you can't know someone didn't slip in something nefarious. There should be a subset: OOXML-SV (for "Security Validated") and OOXML-SV documents should have to be able to successfully pass validation by an open source document security validator app. Then, LibreOffice can only open and save documents in OOXML-SV format "because we care about security."