For me, I need to open a truckload of documents to feed others. The search engine gets flaky when used heavily, so I defaulted to adding "Date Accessed" to the search window... and that column sporadically disappears between search uses. Even adding special characters to files doesn't allow just those to be searched for without a ~= (tilda equals) to lock the search. As I had to resort to indexing the file contents as well as the names (since some names were terribly chosen), the special characters just allows them to be "bubbled" up to the top of a list of 200 documents. Even resorting to "subsequently moving" many of these to other folders, there are always the stragglers that need to be found.
That is just the search engine. The other "insult" is I also use Office 2016 at work, but still on 2007 at home. Many issues with Word alone (specifically document formatting... Header 1, Header 2, yada yada) have not been addressed in the past 9 years. Some have workarounds (carried forward from Office 2007, and others are simple minefields you need to know "do not ever do this!"). Change control can become a nightmare quickly.
There are also a handful of security overlays that were written in Win7 and still not updated for Win10. Most of these fall into the lap of vendors, but after a year I would expect this not to be a relevant issue. Microsoft has a vested interest in the outcome of this one.