You only linked to the "extensions" MS added on top of OOXML, whose specs are in total an order of magnitude bigger. ISO/IEC-29500 or ECMA-376 is the actual spec, and its first part (of 5) is 5000+ pages. In comparison, 349 pages for the main spec + a 9 page auxillary spec for the document "filesystem" seems almost trivial.

http://activityworkshop.net/rants/ooxml.html

The PDF spec is 1000 pages. Nobody seems to complain. Or at least they complain a lot less.

Fortunately the only people who can read 1000-page documents are those who already have working PDF renderers, so the problem is self-limiting.

You can ignore about 800 pages of that for most applications though.

Not really, when you start to implement it, the more and more functionality required as you get more samples.

Much nicer? Not really. It literally a transpilation of the binary format. The XML files a very abnormal for everyone but who are familar how the original older doc/xls/ppt fileformat works. E.g. Look at how the Bold-tag is implemented, no sane developer would implement it that way. It's clearly done to mske it as straight forward port of the old format and make it as difficult as possible for every one else. The XML even contains binary blobs and all. A low-light. Every other modern Office format is nicer.

https://en.wikipedia.org/wiki/Comparison_of_Office_Open_XML_...

https://en.wikipedia.org/wiki/Standardization_of_Office_Open...

Worse, it's designed in a way that works completely differently from every other XML office format to allow Microsoft to patent it. Doing document markup the normal way in XML has too much prior art to be patentable (though that didn't stop Microsoft from trying), but they managed to get a patent on their oddball way of doing things.