In my mind not niche means having jobs, and Rust has no jobs, not in any meaningful amount at least, and none at all in most countries. That puts it deep in the niche category for me.

It's popular in the "let's rewrite X in Rust" community which are very actively posting on HN, Reddit and wherever they can. That gives the impression it is not niche.

But the moment you search Rust on LinkedIn, you can see the truth.