I'd refine that slightly: marketing is telling an interesting enough story to get an enquiry, sales is telling a relevant enough story to get the action.

Communicating the complexity of the product is only part of that. It's the "so based on what you've told me about needing to replace x that takes y hours per week, this z minute process I'm walking you through will generate u more v". For simple, universal value propositions you might be able to turn that into a calculator on a product page, but a lot of value propositions involving salespeople aren't simple or universal. (Also there's the navigating large organizations bit and the outbound bit, but they aren't competing with or complimenting this product)

Ironically one of pclark's comments elsewhere about Journey's value proposition being "so meta" makes me think that's exactly the bit a good salesperson solves for you: figuring out the gap in the specific client's marketing capabilities that Journey can fill