Simply put, he's been doing the same thing for to long. I honestly can't tell the difference between "Blitz," "The Mechanic," and "Killer Elite" because they all feature him beating the shit out of dudes while he he wears dark colored clothes. That's a rule, he can only wear dark clothes. But seriously, what is he lacking, how come I'm not 100% on the train?
It's cause he's not fighting monsters or boxing.
Arnold. His first big movies had him playing a cyborg killer machine, chopping up giant snakes, and fighting intergalactic bounty hunting aliens. That's how you prove you're a badass, you take it to the next dimension, not the next level.
But what about Stallone? Stallone thinks Statham is the next great action star, this is a fact (Stallone once told me this himself) but while Stallone hasn't slayed as many monsters as Arnie, he's got his own genre: the boxing film. Stallone made many of them (perhaps you know this) and Statham should as well. It makes the audience see you as more as an underdog of the working class, instead of a top dog of the assassin with an accent class.
Of course, there's one thing that I know you all are thinking: "The Expendables!" Yeah. Whether it's the ridiculous basketball fight or the fact that he has the most kills, Statham owns that movie. However, he does have a legendary cast with him that provides some type of cool action multiplier (this happened to Arnold in Predator FYI). "Killer Elite" on the other hand has him paired up with De Niro, who I see as serious thespian, and with Clive Owen, who is cool, but has always been afraid to go full badass.
So basically, Statham just needs to switch it up a little bit. And based off this article he should star in a movie with a plot line something like this:
The US Olympic boxing team is recruited and trained by the US Government to to protect earth from an invading alien force.
Sign me up for that.