On the other hand, 1 person who knows AWS well today can do things that would take huge capital investments and a team of 40 people 20 years ago
At a smaller scale, I love Heroku for prototype apps, and I would absolutely use them for a startup - right up to the point where I'd be paying the equivalent of 1-2 full-time devops engineers. At that point, it becomes worth it to hire them and transition away. AWS has a similar value proposition, but the tipping point is higher; I'd estimate it at around 15-20 FTEs in Amazon charges before it starts to make sense to leave.
Rolling your own infrastructure is in a lot of ways def easier than rolling your own programming stack today.