I see one big reason why mind uploading might be practically infeasible and
completely useless excercise.
There is no reason for it to be impossible, of course. The mind, the consciousness, and what defines you as you are nothing more than information, and so naturally the information can be stored and recreated at will. In theory.
However, there is one big obstacle. Unlike a computer, where there is a clear distinction between software and hardware, in a human there is no distinction between the brain and the mind. A lot of the information that defines you as a person is probably rooted in the structure of the brain, and in the way it functions. It might be impossible to separate the two, and it might be that your mind is so tuned to your own brain that you need a full physical simulation of your entire brain to copy it. Worse yet, it might turn out that the copy of your brain deteriorates just as easily as your real brain, making such a copy useless. Or that it becomes a completely different person because the simulation is inexact.
Finding ways to physically preserve the brain and stop any brain deterioration might be a much more meaningful task. I still don't see how copying it to a computer helps you much with anything. And if you want to make copies of yourself, making physical copies might turn out to be simpler.
Not to deny uploading your mind to a computer completely – it might turn out to be one of the possibilities, but I don't think we need to focus on it when there are much more promising things to do with our brains.
Besides, why? We die to leave the world to the next generations. I don't see a particular reason to stick around forever. Although I would not mind getting frozen for a couple of hundred or thousand years right before my death to see the future in my final weeks.