system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Why couldn't Voldemort or his Death Eaters be dispatched easily with sniper weapons or firearms? Bullet would surely reach their targets before they had any reasonable amount of time to react...

Protective spells AFAIK such as protego and others only work on protecting from attacks based on magic. Even if that wasn't a factor, offensive spells that use physical force to harm would pale in comparison to a heavy machine gun or any weapons that use explosive projectiles.

There's also the distinct advantage in the fact that Voldemort and people supporting him would never think to adopt it first and never expect it to be able to take them down. They would also be very hesitant to shift their tactics or adopt it to fight back.

Using muggle technology to defeat Voldemort would also be a perfect rebuttal to his claims of absolute magical-blood supremacy and superiority over muggles.

Good use of tech. like firearms could deal a brutally effective surprise first strike.  Mobile phones would allow his opponents to communicate with impunity and so on and so forth. If there is high level government complicity in allowing magical people to co-exist with muggles like the Ministry with the muggle Prime Minister, than arranging something like an air strike on the most dangerous dark wizard of all time doesn't seem too unreasonable either.
gpt
Listen, kid. It's easy to say stuff like this, because in hindsight, it's seems obvious. But you just weren't there.

Wizards at the time didn't know much about firearms. Most were under the impression that the tech hadn't advanced much since the days of the Statute of Secrecy. Bullets fired by "flintlock pistols" are easily dodged by any decent fighting wizard, or could be caught by a quick spell to stop the metal ball. 

The Magical community doesn't keep up with Muggle advances. It took us decades to appropriate cars, which are only in use for a couple of years. 

> Using muggle technology to defeat Voldemort would also be a perfect rebuttal to his claims of absolute magical-blood supremacy and superiority over muggles.

Most wizards back then (and even now, unfortunately) don't think highly of Muggles, even if they didn't see a need to kill them. Muggles had the same rights as a cute pet.

Also note that a lot of tech you mention wasn't exactly available to the larger public during the First (or Second) Wizarding War.