1. It have no edge, its not the best system language, and far from a good application language (mainly because of the eco system)
2. Fragile community, low number of user and the community forum is toxic frequently
3. It doesnt have strong leadership, D doesnt have a good roadmap, and constantly changing vision
4. Its a big language, and considering the drawbacks, its too big to have such critical drawbacks
I cant really think of any solid reason, why anyone would invest in D, except if they are already knee deep into it for some historical reasons
D is not a horrible language, but today there are so many better choices, and the language is too big, to risk investing in it