Getting a site to load quickly isn't that difficult from a technical perspective. You just need to strip out everything that slows it down. If you can deliver a page of HTML and inlined CSS that renders without JS or images then your site will be fast (or at least it'll be perceived as fast, which is fine.) So long as you're using some fairly reputable hosting infrastructure (AWS, Azure, Google, etc), and if you're rendering on the server you're not doing silly things on the hot path, then you don't need to worry about speed.

The hard part when it comes to site optimization is persuading various stakeholders who want GTM, Clarity, Dynatrace, DataDog, New Relic, 7 different ad retargeters, Meta, X, and probably AI as well now that a fast loading website is more important than the data they get from whichever of those things they happen to be interested in.

For any individual homepage where that stuff isn't an issue because the owner is making all the decisions, it's fair to say that if your site loads slowly it's because you chose to make it slow. For any large business, it's because 'the business' chose to make it slow.