Fortunately for Doctor Who love shooting at people, they're not very good at actually hitting anyone they aim at. Daleks take great delight in exterminating their enemies and, as far as they’re concerned, everyone is their enemy. But the Daleks have one big problem that seems to cause them a great deal of trouble.
Among the oldest and most enduring villains of the entire Doctor Who franchise, each Dalek is a creature inside its own personal tank, complete with artillery. While their standard fittings are a gunstick and a manipulator arm, the two weapon slots on a Dalek's armor are interchangeable and can be swapped for whatever weapons they need. First conceived while World War 2 was still fresh in the minds of audiences and writers alike, Daleks aim to exterminate all other life in the Universe because of their obsession with purity and conformity, believing themselves inherently superior. Interestingly enough though, while it's common for fictional villains to have “stormtrooper aim” when trying to shoot the heroes, this trope actually makes sense for the Daleks.
With only one eye, Daleks have no depth perception. This gives them a disadvantage when trying to aim their weapons, especially at moving targets. They may like to shout and rave about how “Daleks are supreme” but, in of marksmanship, this does not ring true. Canonically, their armor includes targeting computers to help them aim, but this naturally has the same problem as a camera using auto-focus here on Earth — mostly reliable, but taking a moment before it works effectively. Perhaps this is why Doctor Who's Daleks are particularly bad at hitting those who are already trying to flee. It’s likely that any time they do so, it’s largely down to luck. Evidently, this is a difficulty that even a super-advanced alien species cannot work around.
Why Daleks Are Still Major Threats In Doctor Who
Biologically speaking, this actually goes a little deeper. Many creatures on Earth have two eyes, which gives them an inherent understanding of depth. Humans, even those with visual impairment, are neurologically wired to intuitively understand depth. This is why, even using only one eye, a human can gauge distance accurately. Daleks, on the other hand, would have no understanding of depth perception due to their physiology. It’s very likely that the concept simply doesn’t exist in a Dalek’s brain, any more than humans can understand what it would be like to have four arms.
With each Dalek spaceship as powerful as the Death Star from Star Wars, Daleks are clearly not subtle creatures. They very likely don't care that they have terrible aim, because it gives them an excuse to keep shooting. The Executioner Daleks take this even further, with their machine-gun-like heavy repeating blasters. What Daleks lack in weapon skills, they make up for with sheer brute force, backed up by intimidation and strength in numbers. Their weapons have been shown to be devastatingly powerful, and their armor plating and energy shields make them almost completely invulnerable to most weapons. For most beings they might encounter, human and otherwise, the only option when encountering a Dalek is to run. Considering how sadistic Daleks are, they probably enjoy watching their enemies flee in terror.
The most iconic villains in Doctor Who, Daleks are the arch-nemeses of The Doctor and the Time Lords. The fact that humans are naturally better at aiming weapons may provide a little comfort, but it doesn't make the word “exterminate!” any less intimidating. Over the years, they’ve seen many variations, redesigns, and evolutions. It seems that, much like The Doctor, the Daleks of Doctor Who will always keep regenerating into new forms.