I typically report companies that violate this (Chase, I’m looking at you with your “transactional” emails that are just thinly veiled ads) to the FCC (there’s an online report form) but I don’t know how much it helps.
You use unsubscribe for anyone with which you have some sort of prior relationship. Anything else is spam, report it and move on.
Sometimes it's understandable that someone wants to simply filter these mails as spam than go through whatever convoluted process they have in mind for unsubscribe. It's easier and discourages the practice of signing people up to random newsletters.
Years ago I worked at a large email service provider for bulk mailings on behalf of large customers and we took unsubscribes very seriously.
And for the really truly spam/scam emails, the unsub link is the least of your concerns since delivery and tracking pixels confirm the address is real and being used. The true spam usually doesn't even have an unsub link. In those cases mark as spam and hope that your email provider starts flagging them as spam before it ever makes it to your inbox in the future.
I'm an aggressive unsubscriber and 99% of the time it works. Very little junk flows into my inbox these days.
Does it work in Gmail? Since it doesn't load images until I athorize: https://i.imgur.com/RZ93VIU.png
Last time I went searching, I found google documentation that said there are no image options for the iphone app.
Although note that IIUC the gmail default is now loading remote content. (Although they do load it via a proxy so that your IP isn't shared).
I use Thunderbird, which doesn't load that stuff.
I'd rather receive the mail and let Gmail put it into a blackhole than try to solve the problem upstream myself and have the small possibility that I either miss a newsletter and get spam anyway, or tip off some system that my email address is "real".
Unsubscribe is your best bet as honoring opt-outs are protected by the CAN-SPAM act.