That's the problem though: The bad players are hurting the good players. I don't unsubscribe from stuff using mailchimp, because I'm just not going to take the time to learn which systems are legit and will unsubscribe you, and which ones are shady.
So in this case, mailchimp is getting marked as spam, even though they are an honest player.
I think that's exactly the right thing to do. If someone wants to make use of your time and attention for their own advantage, they should ask for permission. Someone who does so without asking for permission first is exactly what spam filters are for. It's not my job to help them with finding people that want to read their advertisements.
That's valid, I'm sure I've done the same more times than I know. My general rule is if it's from a brand or site I know I've interacted with or generally recognize I'll spend two seconds to check the unsub options.
If the unsub requires me to log in first, I mark it spam instead. If the link looks fishy and/or I can't readily discern it's of any quality it's spam. If I have no clue why I could've gotten the message it gets flagged for sure.
Luckily for me I get very few emails per month that I don't know why I would've gotten them, so it isn't a painful exercise to give them a chance to not get flagged.
I use Unroll.me[0] to manage the messages I do want to get, but want to check on my own time and I don't want them sitting in my inbox. I'm sure there are other types of services, but I'm generally happy with what they do. They also can manage a lot of the opt-out features as well, not sure if it 'protects' me any more than doing it myself though.
So in this case, mailchimp is getting marked as spam, even though they are an honest player.