You know, as the law requires in the EU
First, it only applies if you collect PII - depending on what they collect, they might not be subject to the GDPR at all.
Second, informed consent is only one of the options that allows collection and storage of PII. There are various other reason that allow collection and storage of PII, among them "Legitimate interest". For example, it is considered legitimate to store webserver logs containing PII (IP Addresses) for purposes of fraud analysis, unauthorized system access etc. Whether a specific collection of data is legitimate under those clauses depends on the specifics of a case (who has access, what's the exact purpose, how long you store, ...) - ask a lawyer if you need an assessment.
Depending on what they log and how they log, they may be either in the clear or in a bad place, but it's definitely not as simple as "the law requires no logging".
Had they not submitted unique user tokens I think you mag be right. However, that's not how the analytics seem to work.
The law does allow logging for a variety of things but in this case I'd say they're in the wrong. They assume that it's okay because they don't track you across websites and that's good to know, but that's not the point.
If you want to log fully anonymized data, without persistent tracking ids and without leaking personal data to 3rd parties en route (so no "send it to Google and they promise to anonymize the IP afterwards") then you're all good (but IANAL!).
The only reason you see all those cookie notices and GDPR consent requests is because so few companies are willing to accept even the tiniest tradeoff in their metrics to protect their users' privacy.
To be clear to anyone reading: using Google Analytics without a non-Google-hosted anonymisation step breaks GDPR. This _has_ been litigated in court in several countries. There's no "ifs" or "buts" about it.
The German DPA has ruled that the usage of Google Fonts on a website broke GDPR because it forced the user's browser to reveal their IP to Google.
I'm fairly sure that an open-source piece of code that you download and install yourself isn't in scope.