Are fillers an option for treating crepey skin on neck?

Several things can be done to help improve the texture of skin on the neck. Hyaluronic acid fillers can be injected into prominent creases. Because the filler molecules attract water, some physicians inject them evenly in small amounts over large areas to help improve the look of the skin. Topical hyaluronic creams can be used to improve hydration and texture (for example Teoxane or IS clinical's Hydracool serum). Also, topical retnoids or retin-a can be used to improve texture. Beyond those options are several others, including microbotox (small amounts injected in the deep skin instead of the muscle), IPL and laser treatments, chemical peels, and tissue tightening treatments like Ultherapy. I recommend an in person consultation with a board certified plastic surgeon to assess your options based on your anatomy and current skin care habits. Just realize that when it comes to improving skin texture, no one treatment is perfect, and results are best with combining treatments and repeating them regularly. 

Fillers are excellent tools to fill depressions.  The folds near the nose, the tear troughs of the lower lids, and the folds about the corners of the mouth can be treated well with fillers.  These are areas in which the skin follows the lack of fullness of the deep tissue.  Creppiness is a condition of the skin itself.  Fillers are not useful for creppiness since they must be placed in the deep tissue.  Rather than fillers, other treatments could be considered.  Fractional lasers, microneedling, chemical peels, and some ultrasound machines might be helpful.  If the skin is truly sagging, then a facelift may be the best treatment.  The facelift actually does its best work on the neck and jowls with less effect on the mid face.