Polyfills are a good option in some cases. I, personally, try to stay away from them as much as possible. Once you add a polyfill (e.g. fetch), you' soon realize that you need another one (e.g. Object.assign) and soon you will have a list of polyfills to take care of. The advantage of jQuery in this regard is that it has all these "polyfills" in one place.

I believe that jQuery is not "modular" enough for today's web development environment. The "light" version is a step in the right direction but it's not enough. If one could configure the "modules" needed and download/load a single file/library, it would be tremendous.