The phrase "fruitless endeavor" means an effort or activity that doesn't result in any positive outcome or success. It is a way to express that something was not worth doing because it didn't achieve the desired result. Full definition
But the new recognition that seems to be emerging in Mountain View and elsewhere is that software without control of the hardware can be just as fruitless an endeavor. (theverge.com)
I think the point Minh is trying to make is that when your deals are strong from the get go and profit per unit is high, sweating it out over small and variable numbers can be a somewhat fruitless endeavor. (biggerpockets.com)
But smashing this move already is a fruitless endeavor. (justarsenal.com)