What you learn in any decent 3D CAD software will be easy to translate to another one. Fusion 360 is a great package, but it's not because it has particular features that don't exist elsewhere. You can learn CAD on Fusion and leave it for another package later.

What you'd lose are your designs however. 3D designs don't convert well.

But currently there is no 3D CAD software that is good for mechanical design and has a good and free license for hobbyists.