I have legion installed (well pre-patch at least) on a Macbook 2015 1,3Ghz.
Running on Metal, graphics setting 3 out of 10, resolution maxed. 30-35 fps, 20-ish in crowded areas.
If you can accept lower graphics, then yes, perfectly playable.
Though you can't have your Macbook in your lap, cause it will heat up to much and the processor will be throttled.
Keep it on a desk, no additional cooling needed (i have tried one cooling pad, no improvement).