But you are right about the last part...when the user's UI locks up for a few seconds your email is certain to grab their attention. Just not in the way your carefully designed newsletter was intended to be remembered, though.
Plain text mails work better in every possible situation and are guaranteed to be formatted in a readable way. Meanwhile your average marketing newsletter is almost guaranteed to not be displayed in the correct manner as most decent email clients will just outright block any image content by default, and if your designer had the bright idea to also embed all text in images so their carefully selected font looks nice everywhere, well, I can't see anything without manually enabling pictures and then waiting 5+ seconds to see what the email is even about. And why would I do that?