The three sisters approach made it easier to grow crops as the climbing beans didn't need you to create something for the beans to climb. However it reduces your yields by a lot of all crops (the corn shaded the squash, the beans hurt the corn plant) and so it was a bad idea unless land is cheap and labor is expensive.

That isn't to say the idea is always bad, in some cases it can be good. You need to be careful as what seems good might have significant downsides that are hidden.