Can we use Shapeoko Pro for aluminum milling?

If you are removing a significant amount of material, you should get an SO5 Pro.

While a Nomad can do large parts:

it can take a while.

If you have a space suitable for the space and noise and mess of a Shapeoko 5 Pro, that would be my inclination — the SO is the machine for a shop space, while the Nomad is the machine for an office or spare bedroom where its enclosure for containing mess and reducing noise is invaluable.

That said, you could get a Nomad and use it to make a power hacksaw (for cutting stock) and a die filer (for finishing them).