Probably that they have no vision or plan beyond "we're re-writing the site". Most of them do have professional software experience, so I'm sure they know the basics like "we need a database", "check user's authorization before letting them in to the admin area", and "we need a page to let people search for other users".
But nobody else has put much thought into the specifics.
The tech stack, technical infrastructure and architecture, development environment and tooling, software architecture, database schema has all been me up to this point.