I would disagree about him failing harder each time. I think Elysium is absolutely his worst film – it is his biggest and most conventionally mainstream and, perhaps as a direct result, feels the most compromised and sloppy. I'm in a weird minority that quite likes Chappie, though; I may even prefer it to District 9, actually. And I do look forward to checking out his new one, Demonic.
My major reservations about him taking on an Alien have less to do with his specific body of work and any patterns within, and more to do with some or the specific ideas present in the concept art tied to his project.