Yes, a lot depends on the product. At some point, it begins to advertise itself, but before this moment advertising is necessary.
Often, projects that go to ICO launch advertising their product, without having a working prototype and even a less competently designed smart contract. To make the advertisement really effective, the project should have a ready-made prototype, otherwise it's money wasted.
Not everything is so straightforward, some investors believe in the idea, some in the team. The product often means little.