In "the good old days", you would just import a script using a normal <script> tag, it would do stuff on the page, and you're done.
What a lot of people refer to as "modern" web front-end development, there is a whole toolchain needed to compile and prepare your site for deployment: babel, webpack, etc. While these front-end tools solve a host of problems, they also introduce a whole set of new ones, mainly around complexity and the fact that what is actually going on "under the covers" is a lot more opaque to the front-end developer.
You know, when you had to support ie6 and php was cutting edge, the good old days!
I jest of course, but while frontend tooling has gotten quite complex, there's a good reason. Transpiling, minifying, and tree shaking are non trivial, and pretty much a requirement if you want to build a rich client (though not everyone needs one).
In "the good old days", you would just import a script using a normal <script> tag, it would do stuff on the page, and you're done.
What a lot of people refer to as "modern" web front-end development, there is a whole toolchain needed to compile and prepare your site for deployment: babel, webpack, etc. While these front-end tools solve a host of problems, they also introduce a whole set of new ones, mainly around complexity and the fact that what is actually going on "under the covers" is a lot more opaque to the front-end developer.