Most people would agree with you, but i always found it ridiculous (meaning, actually false) when people criticize good action movies for not having a plot. To come up with good action scenes, the events have to flow together in a logical sequence, or it gets boring. In some shitty action movie, the camera jumps around from shot to shot just showing disconnected scenes of mayhem. On the other hand, a movie like DREDD shows skirmishes unfolding over the course of many shots, each of which follows and builds on the last.
An example would be the part where they trap Dredd and set up the heavy artillery, blasting the whole floor to hell... there are a lot of parts to this scene, from the initial "oh shit" moment where he realizes they've trapped him, to the unveiling/setup of the guns, to the tension-building scenes where everything is getting ripped apart, and then finally the "a-ha" where he realizes he has to breach the side of the building. Then, you think they've finally escaped, but in a cruel twist they can't get down, and have to go back in, and so this conflict resolves and segues nicely into the next chapter of the film.
This is all part of the plot, and I think a sequence like this is actually a lot more "plot driven" than most...
finally, this wasn't an american film -- it's british 
I actually thought the first 5 minutes were good, the lead in, societal breakdown, mass civil unrest and rampant crime and the whole cops come judge/jury executioner bit, but once Dredd got caught in Peach Trees, a 200-storey slum tower block and was locked in and become the hunted, I immediately thought 'really', that's what your doing with the movie, the movie was then ULTRA predictable and disheartening as you knew the remainder of the movie would be about the heroic good guy with his unbreakable will and determination somehow surviving 1000 bad guys all trying to kill him on their own turf with the good guy triumphant against all odds.
That scene you described where the bad guys trapped him on the 76th floor and blasted the shit out of it with seriously powerful mini-guns that literally knocked over walls, killed all the residents on that floor but yet somehow DREDD just simply outrun the bullets and remained 6 feet in front the whole time. It was some serious roll your eyes moment, I know it's a movie, but fuck, why are the bad guys always this seriously completely incompetent, they managed to create a drug empire, take over a whole building, rig it too be locked down as a heavily armed fortress, but shooting straight and killing one man is too much too ask, even though every bad guy in the building was gunning for him. I can see how the 13-20 year old demographic might like this, but for this old man, it was a struggle to stay awake to see the more than predictable finish. I'm giving this movie 5 stars out of 10.
