Games can indeed travel trough word of mouth but that is pretty rare. Instead promotion should be done all along the development journey for example you post updates about your game and make people want to get it. This way you don't have to promote heavily on launch and you have a smooth landing into the itch io algorithms.
Although if people like the game it doesn't need promoting. My game ThereIsSomeoneInTheAttic was very well received. It was a weekend project and I didn't promote it at all but people liked it and put it in their collections and now it's getting like 5 views and 1 downloads daily without any further promoting.