So Microsoft are emulating an archaic and impractical form of information presentation and calling it modern, how typically Microsoftian. Unless of course, this is a rare example of Americans using the word 'irony' correctly, in which case, bravo!
The definition of modern that they use does not mean "The newest design that has never been produced before". Their definition falls more under the lines of zeitgeist, where it is the design that represents the common theme of the current time we live in. This is of course completely subjective, but if you look at all the flat design that is out there it can be argued to be true.
As great a job that Microsoft has done with maintaining compatibility with legacy apps, at some point you have to introduce something new. I'd like to see a new systems API on top of the kernel that is object-oriented, and perhaps has single-level store and is processor architecture agnostic so I only have to ship one image for both Intel & ARM.
Something like the way GDS Design Principles is laid out strikes me as a modern approach. Clearly written, responsive, and designed for the web.
This, on the other hand, is a complete turd. Obscure, only readable on a desktop, and has walls of text. Reminds me of the full flash sites of the early 00s.