I think the use of the word 'failure' is being used on the 20,000 feet view of the film's ultimate goal which is to make a ton of money, which is realistically drastically underperforming for Sony. In the studios eyes I think this film is far from the success they were hoping.
In terms of the mainstream, the fans that have come out of it and children it's touched and affected... a total win for them. And that's great! All kids need their heroes and you can't take that from them.
On a costuming scale... you know it's weird.... I don't approve on this film personally, but I have to say I wouldn't at all roll an eye at the costumers sporting the new suits. Ghostbusters as a whole is great. I just feel the new movie is all kinds of wrong and not what it could have been. It'll be nice seeing a mix of men and women GB costumers sporting their own custom suits at cons. I fully support that.
You are right, it touched some young children's lives and might have become an instant classic to them. That is s win in a way.
Look back at some of our favorite films from childhood that might not have been a huge box office success, yet are cult classics to the movie fans of that generation. Look at A Christmas Story, that lasted a couple weeks before it was yanked from theaters. Today it is loved. This could flop today in the theaters but in 20 years it could strike a nostalgic chord in people who saw it as a child, and it could start to grow in popularity. Some day on forum like the RPF, there could be a prop section dedicated to building props from this film. :lol