Personally, I only use external library CDNs during early stages of development, or quick prototypes. There are advantages to having all needed assets locally.

Personally, I only use external library CDNs during early stages of development, or quick prototypes. There are advantages to having all needed assets locally. The main point for me is to minimize external dependencies during runtime - fewer points of failure. Also, vendor libraries can be a single minified bundle served from the same domain. In production they can be moved to a CDN, i.e., CloudFlare. Using NPM makes sense once you start having more than a few dependencies, or a build step. On the other hand, if you can get by with library CDNs and don't feel the need for NPM - I'd say that sounds fine, to keep it simple and practical.