Is there anything that can be done about my sloping/sagging neck? (Photos)

It's best to begin by consulting with a surgeon in-person to discuss your options. Depending on the level of laxity, the effects of a neck lift will certainly outlast the effects of non-surgical treatments. Non-surgical procedures can only temporary resolve the issue and require few to several attempts or treatment appointments. The presence of banding down the front of the #neck, and, amount of excess skin and condition of your skin are among some factors which determine if you are a #candidate for #rejuvenating the neck.
During your initial examination, your chin will be evaluated along with the neck and jawline. A weak #chin implies a lack of chin support for the skin along the neck line. In younger individuals a chin implant alone is usually all that is needed to improve the appearance of the neck. Subsequently, it will also improve the overall #balance of the face and can create the illusion of a smaller nose. As a stand-alone procedure, chin augmentation can be performed in the office under local #anesthesia. For individuals with signs of #aging in the neck, a chin implant added to one of the recommended procedures above, will provide optimal results.
If you are not a candidate at the time of your #consultation, your board certified plastic surgeon can recommend alternatives to address your concern. Consulting with a board-certified plastic surgeon who specializes in #neck lift procedures is important to ensure you are receiving the best advice, care, and surgical experience possible.

it is not uncommon for a man to get a little neck tuck under local called a platysmaplasty and is easy to undergo.

It appears that you have a familiar obtuse neck. Anatomical distribution of neck muscles and fat compartments is most likely reason for that. In order to correct current deformity anterior neck lift would be an option. It involves removal of superficial fat compartment (above neck muscles) that seem to be a major contributor to your neck deformity as well as shaping of deep fat compartment located between deeper muscles of the neck. It is possible that some revision of deep neck muscles (digastric muscles) may be needed. Without in-person exam it would be hard to tell you whether all of this can be achieved through a submental (bellow chin) incision. It is possible that small chin implant would further improve neck-chin balance.