I don't envy you! You have a lot to think about in the US. Here in EU, things are totally different. We have adequate basic services for everyone, including access to the Internet. (The government sees to that, it's one of the reasons we pay firm taxes, especially rich people.) Mobile connections are fast, we're now transitioning from 4G to 5G. It's safe to say that the vast majority of the EU-based websites are targeted for EU. This means that loading a block of common library code isn't really worth the fuzz unless your website is meant for users in the third world or US. 30 years ago every KB -or should I say every byte- counted; I remember stuff being coded in assembler just to make it run faster and be able to fit it on a floppy disk :) I'm glad those days are over in EU and we can now focus on UX - including speed perception. I hope some day US will catch up again!