There's the manga, cartoon series, and multiple movies to use for storylines or to draw inspiration from for an attraction, so there are plenty of ways to make this franchise into at least one attraction. Sometimes something without a set storyline is better for an attraction as well, as it allows plenty of creative freedom for the designers to craft their own story that fits even better into a park (see all the Disney attractions based on a simple concept and not a pre-existing story or IP). There will always be people that refuse a product, especially when it is seen as a "nerd" thing, but that's much more of a minority than people that don't know what Pokemon is/are, so that's not really going to weigh into any decision making process at all.