There's an important insight in there that I think a lot of people miss. It reminds me of the old, probably apocryphal, story about the maintenance guy who comes out to visit some machine that's malfunctioning, hears about what's wrong, then goes and hits it with a hammer, causing it to start working again. The business owner complains about the bill, since anyone can hit something with a hammer, so the technician creates an itemized receipt, wherein "knowing the right spot to hit" is the majority of the cost.

So much of anything is knowing the right thing to build and the right way to build it. Everything else tends to be much easier problems to solve. The same thing is true in rocketry. And that's what's so exciting about these startups, they're not just trying to fill the shoes of past generations, they're innovating, they're doing research. They're developing the knowledge base and experience base that will serve as the foundation of a tremendous amount of future work. Once you've developed the fundamental technology components and figured out an optimum vehicle design then you just have scaling up and iterating (as SpaceX has done, for example), which is a lot more straightforward.