I don't know how Death Wish's release wasn't delayed. It is quite possibly the most ill-timed release in the history of cinema. A gun-toting vigilante mows down "bad guys" in Chicago with gags about the ease of getting a fire arm, torture porn, and a heavy dose of lines about what it really means to be a man? Yeah, let's release that two weeks after a mass shooting at a high school that has sparked national outrage towards gun violence, an introspective look at masculinity, and brought out some of the worst this country has to offer. That sounds like a super great idea.
I know these things are planned way ahead of time, but, with digital cinema, studios can and will delay releases just a week in advance. Maybe MGM just gave up. After its trailer dropped at an insanely terrible time near a recent, nationally-reported shooting maybe they thought they'd be in the clear. But after a mass shooting basically happened every week since then they just said, "Screw it, if we don't do it now, we'll never release it."
The worst part about it? The movie would suck no matter when it was released.