I saw a milk that claims to be just that on the shelves. Incredibly expensive and (from what I hear) nowhere near the same taste.
The problem is that animals and plants do “what they do” with incredible efficiency. If you want to do exactly what some evolved thing does best, you probably cannot come close to matching it with technology. A century of aircraft design and planes are not in the same league as birds regarding flight efficiency.
If animal-free milk goes the path that animal-free meat is, they may well be reaching the upper bounds of efficiency already, nowhere near close enough to replace natural animal and dairy.
Which is a bit of a shame (as a meat-eater). I think having outside competition that could truly stand on its own would help reduce the corruption of big ag.