I'm not denying your lesson, of course. To this day we still have some Lunascript in the codebase, and it does create some developer friction that costs real time. In retrospect, I'm sure it seems obvious that we should skipped the language and just built the framework.
However, it's important to understand that the language itself was built mostly by Justin very early in the company's history, and basically no work was poured into it after we hired employees and built out the product. One framing of Lunascript is two guys taking a few months to try a few big ideas out before building a company they want to do the right way. We always knew we would have to compromise on ideals once we moved forward, but we wanted to see what stuck. I think a lot of the reason we're under scrutiny here is because people look at the time since D+J left Facebook and are like "what did you guys do with all that time?" The answer is the company didn't get started in earnest until almost a year later when we hired Greg and Malcolm.