I think D is not that bad, it's very nice . But it looks like there's no market for another programming language and they have big competitors (C# from MS, Java from Oracle, Go from Google)
Make no mistake D had (has?) enormous potential... from looking at the compiler design and the keywords etc. I'd say it's a really good language. It is basically C++ with *real* strings... just what the doctor ordered. Excellent work, very well done.
Where the author made his mistakes were:
1) Opening the library devlopment to the "open source" community who then proceeded to shovel tons of crap into what should have been a base level language extension. The library should have been very minimal, not the "everything including the kitchen sink" version they have now.
2) Not importing Windows headers directly. The process of converting several hundred headers and libs also got left to open sourcers many of whom tried to write windows imports from linux, creating a huge jumble of files that either don't work correctly or can't be compiled at all. To the best of my knowledge there still isn't a complete set of imports for Windows... He should have simply written it to connect directly to the SDK headers and libs. He could still have incorporated his modules as well and they would have been terrific for developers working on large projects; the way Pascal developers did.
Take away those two mistakes and I'd be using D right now.