All I can see is that your doctor is following the accepted protocols for treating fallen arches. This site pretty much summarizes what all the others say, that:
“Adult-acquired flatfoot is common in women ages 45 to 65. As the condition progresses, pain and tenderness in the arch are frequent symptoms, as well as a noticeable flattened arch. When the deformity is more severe, patients lose range of motion in the foot and ankle and are unable to rise up on their toes at all or without pain. At initial stages, the ACFAS guideline recommends that patients with flatfoot caused by PTTD can be treated with custom shoe orthotics, soft casts, walking boots, physical therapy and non- steroidal anti-inflammatory medications.”
“When initial treatments fail to bring improvement, or if initial improvement deteriorates, surgery may be considered. In cases where the initial evaluation and treatment were provided by a primary care physician, referral to a podiatric foot and ankle surgeon is strongly recommended.”
Other sites simply say that surgery is the last resort but that it is “reasonably successful,” whatever that means. The New York Times says “If a fusion is required then there is some loss of ankle motion, especially turning the foot inward and outward, but otherwise patients with fusions report tremendous improvement in pain and function.”
As someone who has had foot surgery I can tell you that even with relatively successful foot surgery (mine were bunionectomies) things won’t be perfect. In my case, the surgery on my right foot went beautifully. However, the surgery on my left foot improved my situation somewhat but created new problems that keep me from ever walking without orthotics.
I would say that if you truly tried everything else, then surgery might be your solution. However, you might try getting a second opinion in that different doctors favor different treatments. If you do have the surgery you will not be able to walk at all for something like six weeks and you may not be able to drive either. You will have to be careful of your operated foot for some months longer, and it probably won’t be fully healed for about a year. Odds are you will have some improvement in your foot, but it won’t be perfect. You will probably still have problems and may still have to wear orthotics.
However, if the choice is surgery or wheelchair, then I would consider surgery. Good luck whichever way you go.