I have mixed feelings about this. On the one hand, no one can argue with the idea that it takes a ton of work in many different areas to create a successful business. However, this doesn't mean that there's no such thing as a tipping point.

In my experience, many of my projects build on each other, and in many cases the true benefit of each project isn't clear until some critical mass of other projects have also been completed. For example, I spent the first few months of my business making what I thought was a pretty good product, but when I launched it, no one signed up. It turns out that my landing page sucked, I did a terrible job of onboarding the user, and the product didn't come with the right default settings. All of those things were important, but when I finished the last one, all of a sudden free trial users started turning into subscribers. That final project wasn't actually "that one thing" but it looked that way because it was the straw that broke the camels back.

So yes, there's probably not a "one thing" that will be responsible for taking you to the next level, but there will possibly be "one thing" that puts the finishing touch on a massive body of prior work. I think that's the dream that many of us use as motivation for pushing through the tough times at a startup.