Do you know why modern sites are slow? Because time isn't invested in making them faster. It isn't a technical problem, people take shortcuts that affect the speed. They will continue to do so unless the website operators decide that it is unacceptable. If some news website decided that their page needed to load in 1s on a 256Mbps+10ms connection they would achieve that, with external ads and more. However they haven't decided that it is a priority, so they keep adding more junk to achieve other goals.

It's simply Parkinson's Law

And they aren't going to decide this is a problem that needs to be fixed since people will keep using it anyways.

Exactly this, and it's happening everywhere in the software world.

Why bother writing binary search? Linear search is fast enough. Why bother sharing pointers? Copy all the strings. Easy. Data compression? Forget it. Deleting files is totally irrelevant, etc, etc.

Here's another way of looking at it. As long as you're below a certain threshold, users would much rather you implement 5 new features than spend that time squeezing 100ms on the load time.

Another related side-reason why it's slow is we use higher and higher levels of abstraction, exactly to increase development velocity and be able to add more features quicker. I could write a native app in pure assembly and have it be blazing app, or I can write a webapp on top of web frameworks running in Electron, but in a fraction of the time. As long as my app is usable, I'll get all the user while the other person is still trying to finish their app.

lol. How about a 1.5 mbit per sec DSL line?

Might have to cut some features but the point is the same. Companies will build sites to the level of slowness that they think is tolerable. If their user's internet connection gets better that means that they can be less efficient and add more features.

Facebook desktop web is far from being optimized. On my fiber connection & high-end non-Mac laptop, loading "Messenger" tab takes about 15-20 seconds.

Having said that, FB and Google properties (like YouTube) have insane edge over the rivals by having full control over the advertising stack.

Facebook and Google properties (moreso than google.com) are among the slowest major sites.

Something strange is happening if messenger takes 15-20 seconds. You should investigate further.

As someone working on improving we vitals metrics, ad networks are 100% the biggest issue we face. Endless redirects, enormous payloads, and non optimized images. And on top of all that, endless console logs. I wish ad providers had higher standards.

JS whitelisting and ad blocks anecdotally confirm this.

The number of sites that will be loading images and js from three or four or more different ad/tracking and CDNs is nuts, plus the various login and media links, and I feel zero guilt for not participating in this advertising insanity.

Tightly put together pages with only a handful of JS loads are damn near instant over gigabit fiber.

Cannot fully agree. I use adblockers since their invention. Twitter and reddit need more than 5 seconds to load for me on mobile wifi. Ads have their impact but it's not the sole problem.

You had me until the end. I still see significant lag and mismatches on Facebook's page from simple actions like pulling up my notifications or loading a comment from one of them. For the later, I see it grind its gears while it loads the entire FB group and then scrolls down a long list to get to the comment I want to see.

(This is on a Macbook Air from 2015, but these are really simple requests.)

I agree on the Ad Networks causing massive site bloat.

However, in terms of Facebook, I'd say it was well optimized considering its complexity prior to the recent redesign. But ever since the new design, my Macbook Pro can barely type on that site anymore. My machine has a 2.5 GHz Quad-Core Intel Core i7 and 16 GB of RAM.

That's pretty sad. Responsive design is a great idea, but in terms of how it is sometimes implemented you're getting X numbers of styles to load a page.

I think the reason why web sites are as slow as they are is because they can be. Double the speed of the Internet and all computers and soon enough the content will expand to be just as slow as before.