Tracking pixels are the closest we have to determining whether somebody opens (& hopefully reads) the email. Click rate is the next best thing but unless you are an incredible marketer it will be far below open rate, possibly 1/4 or less. What Google is implying there is to use tracking images and automatically unsubscribe users that don't load them after several messages.

Google is not explicitly saying to use tracking images. That might be the only possible implementation of this advice, but they're not explicitly telling you to do this. Also, consider their use of the word "consider". It's not a hard rule to them.

And personally, I still think it's a bad idea to automatically unsubscribe people who are interested in your newsletter merely because they're not loading images. At the very least, make it very explicit that you're going to do this, and maybe give them the option to turn the auto-unsubscribe off.

I'm glad you agree that it is indeed considered a best practice to automatically unsubscribe someone who legitimately subscribed, when they don't read your emails.

I guess blindly assuming that I agree fits the pattern here. I was actually pointing out that you cannot know whether they read your emails or not. Unsubscribing them before they don't load remote images is not the same thing, and is making a lot of assumptions that will be false for a lot of people.

What else do you think Gmail means, when they give those recommendations?

Using a tracking pixel isn't perfect, but like what peter said in another comment somewhere here, it's the best we've got. If you want to implement Gmail's (and other ISPs) best practices, then you need to do tracking of engagement. Just because you don't like it, does not mean that is not considered best practice. Just because it won't be 100% perfect, does not mean it's not considered best practice.

You may disagree that it should happen, but you cannot factually say it is not a best practice.