There is a clever way: if you have to hit the network to make many requests for tiny data, you could batch the many small requests into a few larger requests, and in that response include all data you need for the tiny requests. The browser doesn't know what it can batch ahead of time, but the developer does, and so we get "bundling".
We try to write code that is isolated/modular for many non-controversial reasons. A common strategy is to co-locate related functions/classes/logic in one file and keep this separate from unrelated logic in other files. The more your code does, the more logic to build, the more files you'll have. The same holds for your dependencies. The more they do for you, the more files/modules they need to isolate their logic. Thus micro-dependencies have few files in two cases: 1) they do relatively little and shift responsibility to your code 2) they do a lot but have already combined/compiled their files into 1-2 files for you, often using a bundler.
ESM is an excellent native solution to referencing logic from other files so you can split & isolate your code when you write it. But this is an authoring strategy, and it should not dictate your distribution strategy.
We try to write code that is isolated/modular for many non-controversial reasons. A common strategy is to co-locate related functions/classes/logic in one file and keep this separate from unrelated logic in other files. The more your code does, the more logic to build, the more files you'll have. The same holds for your dependencies. The more they do for you, the more files/modules they need to isolate their logic. Thus micro-dependencies have few files in two cases: 1) they do relatively little and shift responsibility to your code 2) they do a lot but have already combined/compiled their files into 1-2 files for you, often using a bundler.
ESM is an excellent native solution to referencing logic from other files so you can split & isolate your code when you write it. But this is an authoring strategy, and it should not dictate your distribution strategy.