As is the case with most complex problems like this, the correct answer is: it depends.
In this case, it depends on what the crux of your business is. Sometimes the crux is building world-class technology. Sometimes the crux is customer acquisition.
If the crux of your business is customer acquisition, then an exceptional business co-founder will actually be the most important ingredient to long-term success.
This is one of the biggest weaknesses I've noticed in YC's mantra. In most industries, just building something people want doesn't lead to success - you have to excel at customer acquisition also. And, in these industries, as you business matures, you realize that customer acquisition, at scale, is actually the hardest problem to solve.
In this case, it depends on what the crux of your business is. Sometimes the crux is building world-class technology. Sometimes the crux is customer acquisition.
If the crux of your business is customer acquisition, then an exceptional business co-founder will actually be the most important ingredient to long-term success.
This is one of the biggest weaknesses I've noticed in YC's mantra. In most industries, just building something people want doesn't lead to success - you have to excel at customer acquisition also. And, in these industries, as you business matures, you realize that customer acquisition, at scale, is actually the hardest problem to solve.