Yep, Gmail's spam filters work based on the collective judgment of Gmail users. The core of your and linus' problem is a lot of people use the 'mark as spam' button as unsubscribe button for mailing lists.
I find this trend of "follow the majority" quite disturbing - it's as if they're implicitly saying that everyone should think the same way and punishing those who don't follow. What's spam to me may not be spam to you, and vice-versa.
Then again, having a personalised spam filter for each user would probably consume a huge amount of resources...
As mentioned further up, some scoring works well for many users, but not for all, such as marking eg: Russian/Chinese/Not-spoken-here-by-most language as spam.
I really see no reason for why Google should be so bad at classifying email as they apparently are.
There's a spectrum, and if a given sender looks considerably worse than average, they're more likely to get filtered.
If anything, if a newsletter is getting filtered, it's more likely to be the marketing manager's fault - perhaps they don't adequately monitor deliverability, or they don't test their content, or they don't use activity segmentation... etc.