That poster also mentioned Thor. Their point being that successful films in this genre are usually seen as such when they make around $700 million. Especially ones with this price tag. It was clearly expected to be a blockbuster, hence the budget.
And name recognition only matters if there's quality associated with the brand. However we've seen Superman and Batman films flop. We've seen characters nobodies ever heard of be successful (see: Neo, Luke Skywalker, etc.) And simply being a part of a popular franchise like the MCU doesn't guarantee success. It's not like they all make the same amount at the box office.