The performance story isn't just that the backend is written in Rust. It's also that the front is very lightweight (80kB), that the architecture is horizontally scalable, etc...
I don't see in any of those links a core flaw, a problem in the initial engineering that makes it impossible for the architecture to scale. All I see are some poorly written queries, for which the main devs made a root cause analysis and described how it can be fixed. Is that evidence that the inherent design isn't capable of adequate performance? No, it isn't. It's evidence that there are some small performance gotchas that can be fixed easily, and this is normal for an ambitious project.
But even as it is, yes, it can handle mild traffic. lemmy.ml runs on potato hardware, hexbear.net is an example of an instance which has ~3'000 comments a day, which is roughly the scale of this website, and it runs fine on a single dedicated server.