Yes, I agree with that. When you look at one-man shows like C4, Esenthel or Leadwerks then you can see, that even the smallest team can produce great results.

But when you want to have a complete polished product then it makes sense to have people dedicated to special tasks. It can make sense that one guy works only on the render part (like Carmack does at id-Software). Another one can make tools. And then there should be help by a few people to make tutorials, additional documentation and demos.

So maybe a team of 3-5 people might be an ideal solution. More people could slow down because of too much communication between them.