One of the problems with examples like this is that it gives an unrealistic expectation to non-technical people that large & complex sites are actually quite basic. There is a lot of functionality that a typical user never sees and is often where the complexity lies. And as the "app too busy" error message proves, there is a lot more to a site than it's front end alone and cloning a front end does not clone performan…
> And as the "app too busy" error message proves, there is a lot more to a site than it's front end alone I get at least monthly "our servers are busy" messages when accessing Reddit, and their (redesigned) website is so bloated that it takes great effort to replicate such bad performance in a simple clone. Reddit is the one site where you really can't make this argument, it's bloat incarnate.
It could serve even more traffic if it was less bloated of course.
EDIT: Some random stats from 2019 suggest that they're handling ~1000 pageviews a second on average over a month, and a view can take >100 requests to load. Combine with surge load and you're dealing with some serious requests per second.