For that you probably want unpkg, there might be some other similar alternatives that you can look for if you want. They're essentially mirrors of NPM but they automatically bundle packages up and serve it via http like a normal web JS file.
Some things still won't work because they rely on some server side library, like loading files or something, but you won't want those for web development anyway. You might also find that some libraries don't handle being included as a script very well, but you can instead use the import statement and that will probably work better - use <script type="module"> and inside that use import something from "<whatever the unpkg URL is>".
For production usage this isn't ideal because you're not as in control of the code you're depending on, it's less reliable, and it's more requests than if you just bundled everything together, but not everything needs to be for production usage!
Some things still won't work because they rely on some server side library, like loading files or something, but you won't want those for web development anyway. You might also find that some libraries don't handle being included as a script very well, but you can instead use the import statement and that will probably work better - use <script type="module"> and inside that use import something from "<whatever the unpkg URL is>".
For production usage this isn't ideal because you're not as in control of the code you're depending on, it's less reliable, and it's more requests than if you just bundled everything together, but not everything needs to be for production usage!