An observation from auditing lots of dependency code in JS: it's very, very rare for new large JS files to be created in a version bump.

New large files pretty much only appear in "total rewrite" scenarios, and otherwise almost every change is either a) an increase in size of an existing file, or b) a new file that is fairly small. This does not change with the complexity of the problem domain.

This is of course anecdata, but to me this strongly suggests that large code files are generally just the result of accumulated code changes over time without revisiting earlier design choices, rather than some sort of fundamental complexity that just needs a lot of code to represent.