Just an opinion, but web design and development has become a chaotic mess. There are about a million ways of doing most anything, and with specialties and subspecialties developing around each of them. There’s no way any one person can keep up with all this stuff, let alone master it.
If you try to become good at everything, you’ll spend the majority of your time learning and figuring things out instead of earning money. In the best of situations, most any kind of web development involves lots of problem solving and research which, to an extent, needs to be reflected in one’s fees. On the other hand, you can’t typically expect a client to pay you for learning something that you don’t already have a good deal of knowledge about.
As for Adobe XD, if you want to specialize in an XD approach to web design, that’s fine. If so, you probably ought to plan on learning it inside and out, which is the same with any other niche web design/development product, language, framework, CMS, philosophy, blah, blah, etc, etc.
With web design, there’s always some shiny new thing coming out of nowhere that distracts everyone’s attention. Today, that might be XD. Next year it’ll be some entirely different sort of thing that nobody’s ever heard of.