Labjs

Created before widespread adoption of ES6 modules and native async/defer, making it less necessary for new projects using modern tooling, and the README notes it's undergoing a major rewrite.

The API and configuration can be overkill for basic script loading, adding learning curve and potential errors compared to straightforward native methods like async/defer attributes.

The project is in a rewrite phase to version 3.0, indicating current version may not be actively maintained, and it lacks integration with contemporary build systems or frameworks.

Relies on techniques like XHR preloading and cache busting, which can be fragile and may not work consistently across all browsers, as mentioned in the 'New in v2.0' section about feature-testing.