This seems less like copying a brain onto a computer and more like getting a better understanding of how the brains is structured. Would a human version be a copy of that person, or just a model that can be used to understand how the brain generally works? Even if you capture the full structure of every neutron in a brain, the brain is more than just structure.

A brain without electrical activity is a dead brain, and even if you can simulate activating neurons to see what they would do, it wouldn't be more like shocking a dead animal to see how its limbs twitch. You'd need to use another method to scan the patterns of action potentials that constantly occur throughout a living brain. You'd also need to be able to map how neurons rewire their connections with neighboring neurons from the way they fire and interface with their neighbors (aka the mechanism for learning and encoding information).

This becomes an even greater challenge when you consider that it would likely require invasive surgery to even get that structural scan of the brain, something that could easily kill a person before you had the time to get all the information you'd need. It'd probably be even more invasive to implant enough electrical sensors to actually differentiate individual neurons, and a lot can go wrong. You'd need to scan countless times while also having the patient be alive, conscious, and experiencing a range of emotions and events to more completely understand their specific brain in motion. Needless to say, were still a far shot from truly digitizing an animal, and even further away from being able to scan a person.

Another big consideration is the stability of the world during this time. Enough anti intellectualism or persistently terrible economic conditions could cut down on skilled researchers available. Wars and authoritarianism could cause brain drain away from the long term projects that do this sort of work. If climate catastrophe or nuclear war or an AI apocalypse fucks things up enough, the timeline might be pushed back even farther. People assume that today's world is tomorrow's, and I can personally assure you that is not a safe assumption, even in science.