Obviously everything that can be built by an individual is better that way than if built by a team. But at some point the amount of work becomes too much for one person to finish in a reasonable amount of time (e.g., a lifetime, or before their project becomes out of date).

What I'm describing is not do-able by one person, and the result of refusing to coordinate a team around the project (and instead having a hodge-podge of tools built by various people) is the current LaTeX ecosystem mess.