Action movies have become more of a specialty or niche nowadays. Statham does fine.
That's exactly it. Today's big budget vehicles aren't the R-rated action movies of the Stallone-Schwarzenegger-Willis glory days, studios are more interested in PG13 superhero/fantasy tentpoles. Statham isn't really the same generation as those guys, if he'd been around in the early 90's he would be considered right with those guys and would've starred in a few blockbusters. Instead he's carved himself out a successful niche of making lower-budget but still profitable movies, some of which are really good and some of which are forgettable but are rarely bad or money losers (Parker may be breaking both those streaks though I guess). It's true hes and actor that could do more, I guess it's just a matter of time until he either gets the right director/script for another star turn or takes a supporting/villain role in a superhero movie.