But I think the fact that users opt-in to HTML emails and engage with them far more frequently than text opt-in and engagement indicates that your opinion is an outlier.
I like HTML email. I opt-in only to companies that interest me enough to do so. Those times when I'm opted-in accidentally by not unchecking a box or whatever during checkout I just unsubscribe from and move on. What I have left is useful content in my inbox, some of it more directly sales oriented, the rest more generally informational.
Similarly, for certain senders, I chose to tell Gmail to always load their images — including tracking pixels. It's not a violation of my privacy any more than the numerous pixels on any other website I read.