If those emails are flagged because they’re “conservative” then I agree with you that needs to he corrected.

However, if those emails are flagged because they violate well known spam rules then let’s help “conservative” email senders to follow the rules. Examples include not using single or double opt-in for signup, not honoring or providing an opt-out link, using emails from a bulk list that includes known flagged emails, not including a plain text copy of the email in the message, and originating from a flagged server. Reputable email services like MailChimp go to great lengths to educate email list admins how to follow these rules & curate high value email lists.