In What is difference between XML Schema and DTD?, two answerers state that DTD "is deprecated". One of them, user vtd-xml-author, states that
DTD is pretty much deprecated because it is limited in its usefulness [...]
at which user Jesse Chisholm comments
Deprecated? No. [XDR is deprecated] Going out of fashion? Maybe [...]
In What is DTD exactly?, user AlexR comments on an answer as follows:
Note that DTD is deprecated in favor of the more declarative and powerful XSD.
In this case, no-one shows up to disagree.
So is DTD deprecated, or not? It is surely a matter of fact, not of opinion. Presumably it is the W3C or some other standards body who would have the authority to determine whether DTD is in fact deprecated. Of course, the use of DTD in a given context (for example, a particular software system) might be deprecated without DTD itself being deprecated outside of that (or any) context.