What about using "trustable" dependencies? For small utilities like left pad, you could use lodash. You can import just the function, but still get the benefit of knowing that its lodash so it won't go down, it'll be fast, and well tested.
I suspect JavaScript ended up this way because people wanted to avoid downloading anything they absolutely didn't need in the browser. Now packagers can automatically remove unused functions (WebPack 2 does this IIRC, and I think require.js did ages ago) so it's no longer a concern but somehow NPM still ended up with a million tiny libraries.
Thank god Underscore/lodash didn't use the approach of one-module-per-function.
The difference is they also provide the rollup bundle with all of Lodash. Which is what most users actually use.
My understanding of the left-pad issue was that it was frequently down the dependency tree where dev's themselves could not remove the dependency on left-pad without modifying or branching a dependency (or perhaps multiple).