You're right that the README should be clearer about the beta status and the current feature set. That's a great suggestion, and I'll get that updated.
Regarding the errors you saw, I suspect the main culprit isn't a general lack of PHPDoc parsing, but rather the two biggest remaining features we're actively working on: support for magic _@method_ and _@property_ tags. Mago has full support for generics (@template), assertions (@psalm-assert*), conditional types, etc., but the absence of those two is definitely a major source of noise on established projects right now. They are our top priority and should land in the next beta release.
On the topic of feature parity, you're right that it's a moving target. Our goal isn't to be a 1-to-1 clone of Psalm or PHPStan, but a different tool with its own strengths (see: https://github.com/carthage-software/mago/discussions/379). For example, Mago will flag code like `[0 => $a, $b] = ["a", "b"]` as an error, which other tools currently do not.
We're very aware of the current noise level. We test Mago daily against massive, multi-million-line codebases. On one such project, the first beta reported ~250,000 errors; we're now down to ~30,000. While still a lot, it shows how quickly we're closing the gap on false positives.
Thanks again for the valuable feedback. It's a long road, but we're confident we can reach and surpass the current standards in a very short time.