This is true. All the space engineers I knew were saying, at the time, that scaling wings is a hell of a lot harder than scaling rockets. And it has been. Plus,

This is true. All the space engineers I knew were saying, at the time, that scaling wings is a hell of a lot harder than scaling rockets. And it has been. Plus, air-launch introduces an extra element of operational complexity, and extra manufacturing complexity since you have two lines of hardware with very few synergies between them. These problems could have been overcome, however. They would be left with a more complicated and expensive space-tourism system than is strictly necessary, but there's no reason it can't be done. Overcoming the limitations of their architecture, however, would have required good management. They haven't had that: a quick perusal of glassdoor shows that their management is driven by people whose core competency is back-scratching and accruing seniority, rather than a meritocracy driven by technical and managerial skill. That problem, alone, has been more than sufficient to keep Virgin Galactic grounded. Bad management can kill even the most elegant, viable technology.