You'd be surprised how close this is to the truth, if you ever saw how the sausage is made.
There are few easy promotion-worthy projects left to be done for NT or Win32, so little work gets done. A lot of the work is done by people who don't develop Windows as their primary job description, especially Azure folks.
I heard there was also an internal rewrite of Uniscribe in Rust a few years ago. Never got released as far as I know, but I've been told it laid the foundation for other oxidation projects within the company. Interesting to see this rewrite of DWriteCore, maybe it was inspired by the earlier Uniscribe work.