It took 25 years, but with the fifth and latest entry, “A Good Day to Die Hard,” the series has finally devolved into joyless sludge. The 1988 original remains the very model of a modern action movie: smart, logical, loaded with firepower but rooted in the stressed vulnerability of Willis’s McClane, a little-guy cop against sneering Euro-terrorists. “Die Hard 2” (1990) is almost as good, and if 1995’s “Die Hard: With a Vengeance” is sloppy and spread out, at least it’s fun. With 2007’s “Live Free or Die Hard,” the series was back on firmer footing but also tending toward the ridiculous. That one lost me (and more than a few others) when the hero jumps onto the wing of an F-15 in mid-air.

“A Good Day” jumps the plane, as it were, almost from the start. McClane travels to Moscow to pull his estranged son out of prison and lands in the middle of a high-level Kremlin plot. The Putin-esque premier (Sergey Kolesnikov) wants to kill Yuri (Sebastian Koch), a millionaire-turned-dissident holding an incriminating file. (How do we know the villains need the file? They say, “We need this file!”) Once young Jack turns out to be quite a bit more capable than expected, the expected over-the-top mayhem is punctuated by scenes of macho father-son bonding.

There are two problems with “A Good Day to Die Hard”: It’s terribly filmed and nothing in it makes any sense. Director John Moore (“Max Payne”) stages an early freeway chase with so many pointless zooms and jiggle-cam shots it’s as if he’s daring us to follow along. Maybe we shouldn’t, given that the scene ends with Willis forcing an enormous armored tank off the road while driving an SUV half its size.

Moore also leans too hard on slow-motion, and he even throws in an ’80s-style freeze-frame; someone should take away his DGA card and enroll him in Over-Directors Anonymous. Skip Woods’s screenplay, meanwhile, asks us to believe that anyone can take off the hazmat suit and stroll into Chernobyl once the villains have sprayed a magical anti-radiation potion on the walls. It must be Febreze.

As the son, Courtney comes across like Sam Worthington (“Avatar”) minus the dazzling charisma, and Willis just punches the clock like the grizzled pro he is. Aside from the fireballs and shoot-outs, the first “Die Hard” movies had several things going for them: fiendishly contained settings (a skyscraper, an airport), memorable bad guys, and McClane’s ticked-off weariness. “A Good Day” has none of the above. Even the big seventh-inning twist comes and goes with a shrug.

As always, the cars and choppers and buildings blow up real good. Yippie-ki-yay and all that. But with “A Good Day to Die Hard,” this franchise dies with a whimper.