Shotwell is a great manager, but SpaceX would not be anywhere near where it is today without Elon. I would argue instead that they work together well as a team, and the company wouldn’t be as far along as it is today if one or the other hadn’t been there. However, Elon is by far the most important of the two. Great managers are rare, but not impossible to find. Visionary, technical leaders like Elon are extremely rare.
One of Elon’s strengths is that he makes bold decisions that work out. Building the Nevada gigafactory, the largest factory in the world, was a ridiculous idea for such a small company. Spending huge amounts of money on rocket reusability was so idiotic that no national government even considered doing it the way Elon did it (the space shuttle was the government’s solution, a committee design if I ever saw one).
Make no mistake, Tesla’s value would diminish significantly if Elon weren’t there.