Actually I agree with this, perhaps we're just debating cause and effect. Developers in my experience do hate putting together html email due to the wonky client constraints and as a result often say to marketing "its a mess, I don't want to touch it, find a e-mail making program / service to do it".
But is that the cause or the effect?
Rather, are email clients still a mess because developers don't have much interest in topic? Even gmail has strange html/css rules, if google pulled that with chrome there would be pages of developer outrage here on HN, almost no one seems to care about gmail's html rendering, or enforcing a spec/compliance for email clients, developers are apathetic about it.
What I'm saying is, developers don't like working with html email because its a mess, but its a mess because the development community as a collective doesn't seem to care about it, at least not enough that there is a concerted effort to fix it.