It probably wasn’t a big deal when it was a niche project until Twitter imploded. Then all the public instances got overloaded with new users and the limits became obvious.
A better design is Lemmy which is written in Rust so it has far more scalability. It’s compiled and because it’s tokio / actix based, it can also do a lot more stuff asynchronously so it’s not spawning thousands of threads to cope with concurrent requests.