Absolutely. I work for YC. An artificial kidney would transform the lives of millions of people on dialysis. It's worth trying to build one even if the chance of success is only 1%.
The approach that the kidney project is taking is very promising. It expands on the current dialysis method. Improved filtration but self contained in the body. No need to lug around a heavy machine. No regular clinic visits. 24x7 cleaning of blood. Reduced chance of infection. No rejection issues unlike transplants. The cost savings vs current dialysis is mind-blowing. Back in the 80s, our current dialysis method was in their infancy until new materials (plastics) made them feasible.