The problem of Nim, as a Japanese documentation I've found had pointed out, is that it's useful for a solo-programmer but not for a team consisted of many programmers. The lack of namespaces, main functions and restrictions-on-access makes it hard to code cooperatively, but if you were a solo-programmer, would you like to write `static public void main` whenever you're trying to make a small script? If you were the only programmer of a project, would you like to be forced to mark everything as `public` in order to have the access to them? If the project goes very large, those help structuring the code well, but while the project is not large, those are just annoying features. Those will introdoce a large complexity at the first place, and thus increase the difficultiy of learning. The decision to avoid those makes Nim to be favored by solo-programmers, part-time developers, and students, but not by large companies. However, if it changes, it loses the current market. This is similar to the problem faced by Linux and some other open-source projects, I think.
As for indentation, it's different, as it _increases_ the cost of learning (The learner must first know that "indentation" means to have more spaces at the start of a line, before learning further) and the cost of restructuring the code (one must add/remove the correct amount of spaces when moving a block of code into another place), but reduces the visual burden when viewing the code (especially when the project is small), which I think is worth the cost. As Python continuines occupying the top of TIOBE Index, being indentation-based should not be considered a disadvantage.
