Yeah, it's not serious enough for me. It will become serious if it actually replaces openssl, or at least actually is in use by any significant numbers. Until then, it's a project that can potentially maybe sometimes be used by someone maybe, which by definition isn't serious. Like any other project, it needs time under pressure, it needs to mature with use, be supported for some time, accept patches and changes, and sustain constant prodding by people who would like to break your stuff.
OpenSSL is a standard for almost 3 decades, Rustls is cautiously maybe being pushed in experimental branches.
It's like that with everything Rust related really. We are at a phase where enthusiasts enthusiastically trying to convince someone to consider their new toy, which means we can't really compare it with decades old projects that were scrutinized and stress-tested by millions of people.