that doesn't make sense to me. You don't have surgery because of an MRI. You have surgery because the Orthopedic Surgeon recommends surgery. They use CPT diagnostic codes to order surgery. That needs to jive with not only an MRI but an Orthopedic X-ray and the work the surgeon wants to do. "Instability" - is meaningless. Your Orthopedic Surgeon READS the MRI themselves. They don't use the "read" of a radiologist. The surgeon will use the read to make quick work and know where to focus. Instability is a judgment call and not a professional assessment.
If your surgeon didn't do their part, that might be the problem. If your back isn't bad enough, and your doctors didn't do the required protocol - deeming it unsuccessful - that also could be a problem!

Meh,
Sounds somewhat familiar. It is true, different experiences and training will lend to different recommendations and outcomes.
As an exercise physiologist (also with back issues) I would think how I can use what I know to maintain (and maybe build) on what I have. Bones give shape, tendons provide support, but muscles help keep in place. Nerves tell when we need to address a problem. That's just my take and I am not a doctor.
I might also think that AI is a factor here as well. Just keep working on advocacy and what will work for you.