Maybe this movie is not the superhit we would like it to be, but this doesn't mean to be a flop. Thanks this movie the value of the brand as multimedia franchise has been increased.
I say it is too soon to proclaim to have been a failure. We should await even after the end of this summer.
The movie is fun, but the ordinary audience didn't know yet it is. It shouldn't be a failure, among other reasons because there are worse movies with a better box-office.
And maybe a lot of parents would rather to await to be realesed in streaming service, because it is easier to censor some scenes if they think these are inapropiate for their children.
Do you remember the first movie of Hercules played by Kevin Sorbo? Hercules and the Amazons. Technically it would be a "flop", but thanks this the "Xenaverse" was possible, and this opened later a door for a spin-off with Xena the warrior princess as main character.