To use another IRL example, humans did drive the wooly mammoth to complete extinction with little more than sharpened rocks attached to sticks.
Humanity's ability of cooperation is a massive force multiplier and let's us accomplish tasks that would kill and individual.
At its core DnD is a wargame where we spend most of the game time fighting against monsters and bad guys. Having robust combat systems is the big draw of the game and fighting monsters in interesting ways without being too unfair either way. People want rules that are robust enough to make interesting combat but don't completely break down under a bit of the box thinking, like the peasant rail gun, or the moon box lich, or the create water in someone's lungs to cause drowning, or the coffeelock to get infinite spell slots.
All of these mechanical oversights are frustrating to play with because we have to stop the game and debate over whether this cheesy game breaking bullshit should be allowed at the table and it takes time away from the reason we're all here, to get together play a game, and let everyone have fun, DM included. And sitting around debating whether the moon counts as a container for a lich's soul reliquary or lining up 500 peasants and each of them readying and handing off an object at a bazillion mph for an hour and a half breaks the rules is not fun.
You want a system for magic that encourages being busted even at high levels? Play some Mage the Ascension, you can do some absurdly wacky shit even at fairly low power levels.
World of Darkness and other Storyteller/Storytelling system games call their GM the Storyteller, which I think is a good title for it.
As for why designers make up their own, the term Game Master is pretty generic, and kinda boring, and they want to create something unique and/or more flavorful to their games. The term "Dungeon Master" is also owned by Hasbro and also only really makes sense in more Tolkien inspired fantasy games where heroes are crawling their way through dungeons.
Because certain systems have different focuses.
The core game focus of DnD is pretty heavily directed toward combat. Most of the spells and skills your character has are for combat or for getting into combat or for between combat encounters. It's a combat centric game, with some RP rules added on top for in-between combat encounters.
Compare that to World of Darkness's Storyteller system, which is much more heavily focused on the social interactiom and narrative drama. Combat in that game is quick and usually quite lethal, and even in the 5th Edition games Paradox is releasing, calls for combat to be 3 turns before resolving the interaction.
It takes a lot of time and effort to add on your own rules to make these systems handle what they weren't really designed for.
I wouldn't really want to run a game of complex political intrigue in DnD just as I wouldn't want to run a monster slaying dungeon crawl in World of Darkness.
ROCK AND STONE!
Yeah, gender being a social construct doesn't mean everyone everywhere just suddenly becomes genderless androgynous blobs, we still express our gender in the ways we want to express them.
For example High heels, sheer leggings, long curly hair, and a flowy skirt and poofy blouse adorned with shiny bits. Am I describing the style dress of women today or the style of dress of 17th century French kings?
Certainly coffee houses do have historic basis in our own reality but the highly commercialized omnipresent franchises with extensive supply chains like IRL Starbucks would definitely be a bit more anachronistic, especially in an adveture friendly world where monsters and bandits are waiting outside the walls of the city waiting to ambush cargo shipments.
Something like that probably wouldn't have been even remotely possible until the age of Mercantilism well after the medieval period gave way to the Renaissance and eventually the age of exploration.
What a quaint idea Citizen, as if technology doesn't already pervade every aspect of our world. Why one might think even fleeing to the countryside could protect them but we all know the space race was won back in the 60s. It would be a shame if some highly reflective objects put into orbit a few decades ago were to suddenly shift their course.
I really like WoD's Resources background, one thing I do tend to append to the rules is separate out recurring income from lump assets.
Basically Income Resources are used up and refresh each month worth of time provided players maintain their income or have retainers keep watch over the accounts. Lump Resources are like having a big pile of gold, or a big inheritance from an eccentric uncle or just a bunch of money in a savings account. Once they're used up, they're used up.