Rust isn't great, and it shouldn't be a surprised since it's designed after npm. However one metric where nodes_modules is still worse for me is the sheer number of small files in it.
Having nearly one million files in nodes_modules isn't that unusual. The problem is that on most common file systems the minimum allocation is usually at least 4KB. So even if the actual data is less than 500MB, you end up with 4GB disk space used/wasted.
I wish ext4 had a feature to mark a file as "atomic" where it would allocate all atomic files in a long run, without room for expansion, and I suppose with very inefficient compaction upon deletion, but without any padding bytes.
A file “pointer” for byte exact files, pointer gets ditched for files that get updated or the pointer gets adjusted to another common file.