Some people scoff at mind uploading, human level or greater artificial intelligence or nanorobots that are able repair all damage to the human body

Here is a review of the current state of brain computer interfaces, brain simulation, and nanomedicine related medicine (cellular repair and rejuvenation) and science. I do not see anything stopping zettaflop level computers (one million times more powerful than the current best supercomputers). Zettaflop computers will enable human level brain simulations or greater.

Brain computer interfaces already exist in many forms and are able to restore and create memories.

There is nanoscale technology for precise delivery of drugs, genes and imaging agents into the cells of the human body and interaction with cells.

Adult cells have been rejuvenated

it appears that there is a path to those levels and that it is not unreasonable to expect those levels to be achieved.