Earlier quoted context omitted.
You said it yourself. The tech you're suggesting didn't meet their requirements. Once it does, they will use it. A marketing site SHOULD be optimized for the editor. This is a failure of the dev, not the marketing person.
my confusion is why it's their requirements that need to get met, not say, the readers' requirements.
Them being able to easily change the website is critical for them to be able to do their job. As in most things in life, it is a balance that needs to be achieved and not one thing that trumps everything else.
As others have said, WP gives them a way to easily change the data that they are responsible for. It should be the devs/systems engineers responsibility to make that data present as a static web page using plugins or caching layers and that should be transparent to the marketers.