"It can eliminate the need to deal with HTML5+JS."
I don't understand this, but of course you might be using Lynx to post so you can eliminate the need. Regardless, apparently Microsoft Office is now very complexed.
I'm now concerned by people who send me .xls files in 2018. Is it that people who use that file format think everyone uses that file format? I can't imagine why the same contents can't be accepted as a .HTML file.
A lot of people just want to open a file without having to worry about plugins and possibly versioning. Do I want more than 1 application to open multiple file formats of similar contents? Can't say I do.