That is not problem of Mailchimp, it's problem of culture and "best practices". It's really annoying and it became annoying long before this change.

I receive lots of such emails not only from Mailchimp. At least Mailchimp has one-click unsubscribing, most custom-built mailing list systems don't have it, requiring to log in or just not working.

The problem with Mailchimp is:

- Spam filters work mediocre, despite AI hype. I think they are still based on linear regression on bag of words or something like that. Instead Gmail blocks your server if it sends mail for the first time instead of being large company's server that already sent 1e100 emails.

- Mailchimp exploits this. You can't send email on your own and have to buy their service. It also spreads additional FUD that you must use it, otherwise all your mail goes to spam.

- Gmail treats Mailchimp as privileged sender so if I mark promotional emails from hottest startups as spam, new similar emails are not sent to spam folder.

- Hottest startups know this and subscribe you to all their mailing lists each time they got your email.