Charles Simonyi and most of the BravoX team left Xerox for Microsoft as a group, around about 1982 or 1983. The first version of MS Word, which appeared maybe a year later, was essentially just a port of BravoX to MS-DOS. If you read the BravoX manual, you can see that it already has MS Word features such as Styles. MS Word also shows its ancestry in its native file format. Bravo and BravoX stored out files by essentially just dumping the memory heap. This made saving and loading documents very fast, but it also meant that a) the file format was not at all easy to decode, and b) some strange stuff, such as previously deleted text, is stored out along with live text. These idiosyncrasies of the file format are still present in the current version of MS Word.
Is there really any new software? Obviously there must be, but it's quite rare. All of the commercial and vertical market s/w I know of has strong roots in very old systems. Word's roots go back 22 years. It was a pretty decent application until about 1995/1997 -- not the best, but tolerable. After 1997 a bad design decision mixed up the original Styles model with a different inline formatting model. Since then Word has been fundamentally broken. (Not that most people care or notice.)
Lots of lessons here, including what happens to software when it diverts from the vision of its designers.