The Rock is a charming guy, but they're aren't really stars that can "trick" people into seeing shitty movies anymore. You can make an average, dull movie that caters the lowest denominator and people might turn out. But if you're movie is complete crap, doesn't matter who are, people won't come out. You might be able to get their money on a bad sequel but first time effort, nah.
I feel the same way
People are not necessarily smarter these days, but are way more selective due to factors like higher ticket prices and ease of availability of movies that the masses no longer flock to see big names without something else that looks interesting to go along with them. Not even Tom Cruise could draw people out to see Edge of Tomorrow which had better marketing and ideas more interesting to sell.
The trailers for Hercules look awful, I have no plans on going to see it, and probably won't even bother wasting my time on it down the road when I see it on TV while flipping the channels when it hits cable. That's how much interest I have, and I'm probably close to the target demographic.
I like the Rock, but as big of a star that some people see him as, imo he does not have a standout movie to his name that was the leading role that gives him the enough star to draw big numbers off his name alone. Hopefully Dwayne Johnson finds the right project sooner or later or just keeps enjoying his solid pay days.