I hope everyone is nice and busy setting up encryption, access control and timely erasure for all their server and application logs: https://www.ctrl.blog/entry/gdpr-web-server-logs
'You can’t collect and store any personal data without having obtained, and being able to document that you obtained, consent from the persons you’re collecting data from.'
Consent is just one option. You can do logging without personal data. You might have a legal obligation do to (full) logging. You might have a legitimate interest. And so one …
It is wrong to summarise the GDPR as 'consent is always necessary'.
I'll give you that the article is not very comprehensive, but the GDPR is large and complex and the author doesn't set out to cover it in every detail. What misunderstandings did you see?