LibreOffice needs to pull their heads out of the sand and recognize that both OOXML and ODF are the past.
Make it a polyglot ZIP à la SingleFileZ if you have to (or polyglot JSON[1] or just straight up XHTML with a big sidecar blob of embedded metadata), but nothing trying to take on Microsoft Office is "the future" if it's trying to get there with a strategy shackled to the notion of people downloading the appropriate format-compatible software for something as simple as being able to view (not even edit!) the document that has been sent to them.
It's great to have open standards and free software, but be compatible by default with the universal formats understood by the readers for the ubiquitous document infrastructure that everyone already has installed (WHATWG-/W3C-compatible hypertext readers, i.e. Web browsers), or be forever doomed to the same level of obscurity that OpenOffice/LibreOffice were fated 10–15 years ago due to their myopia.
> A forward-looking format is one that reduces future dependency, not one that reinforces it[…] A “backward-looking” format, by contrast, is one that ties the future to the commercial strategies of a single vendor. In this sense, OOXML Transitional is an archaeological artefact that preserves the past at the expense of the future.
This is delusional. As long as it's modeled on the same outdated paradigm of 80s- and 90s-style office suites (no matter which one), then any format whether it's an ISO standard or not is hopelessly attempting to preserve the past.
The media (web or desktop) is irrelevant: a file format must exists for backup and interoperability. I barely use office documents myself, but I work on software that produce and parse many spreadsheets every day.
An open standard is even more very relevant in public administrations where the process follows legal constraints and ISO standards. The Document Foundation's article reacts to an German institutional decision.
Even today, web formats cannot render documents with the same fidelity as ODF. Especially not for spreadsheets.
Remember, many people feel that neither ODF or OOXML are sufficient and reach for things like LaTeX.
I think LibreOffice also supporting Markdown is a nice nod at simpler open formats.
Perhaps you have not dug into the problem deeply enough.
ODF is certainly better than OOXML at any rate.