There is no special reason that an artist today should feel entitled to apply the fluxus label to their work or to themselves. But there is no special reason that artists working today need to refrain from using the Fluxus label either. Like all labels, the Fluxus label can potentially supply information and disinformation simultaneously.
Labels are like avatars or shortcuts. They are symbols for features common to all objects included in the set described by the label. But because they serve only as signs, many objects included in the set will differ from others in the same set by virtue of other features not common to the other objects. In the case of Fluxus there exist only a small collection of features common to all artists, artworks, and objects - and even this small set is often disputed. That may be why it is more useful to think of Fluxus as an attitude rather than as a movement or a group of specific artists.
If artists say that they produce Fluxus work, or Fluxist work, or Fluxus inspired work, there is a good starting point for understanding their work. If people describe themselves as Fluxus artists, one will (assuming one knows something about Fluxus) have a good idea about the kind of art produced. On the other hand the label in this case might also lead to confusion as the "Fluxus Artist" may or may not have been associated with historical Fluxus. There are really two groups of Fluxus artists. Those who began the Fluxus group (Maciunas, Higgins etc.) and inititated the attitude; and those who continue to create work with a Fluxus attitude. Some of the first group continue in the second group and some do not, while some in the second group began in the first group and others did not.
For example, Yoko Ono is a Fluxus artist who no longer (to my knowledge) creates Fluxus art, whereas Allen Bukoff may also be a Fluxus artist, but he became associated with Fluxus post-Maciunas. Then there is the large group of us who create Fluxus-inspired art which can be described as being Fluxus, Fluxus-like, Fluxus or something else. I don't think that it is inaccurate for any of these artists/writers/performers to describe themselves as Fluxus artists.
I think that the description of Fluxus as "an attitude" remains most useful. It allows for the historical entity of Fluxus that existed until 1978 - while also allowing for the living Fluxus being created from the late 1950s until (and beyond) the present day. Fluxus is (and was) always in flux, changing and evolving, and like Intermedia, it exists in more than one dimension simultaneously. There is the historical dimension, the attitudinal dimension, and a taxonomic (what kind of object) dimension to Fluxus - what Fluxus "is" depends on the dimension being described.
NOTE: To gain a better understanding of Fluxus as an attitude I highly recommend the book, Fluxus: The History of an Attitude by Owen Smith.