So when someone else says they want to play a species that never existed in my world, what do I say? Do I need to include Harengons, plasmoids, firbolgs, loxodons and every other species that was ever introduced as a playable character? Do I have to include shardminds, yuan-ti? What about species from some old third party product?
Well, you work with the players. Presuamble, you have a finite amounts in your campaign, so you might even have to allow shardminds, just one, for the one player that likes the idea, and no yuan-ti at all, because no one asked for them.
Of course, maybe it doesn't actually have to be a shardmind, either. Maybe there is a game feature or a story feature or visual that they like about it and can be accomplished in a different way.
The beauty of D&Ds long history and many supplements is that you basically any character idea probably has had one class or race has precedent somewhere. I could easily see that in an AD&D campaign a player would like to play a Golem (either a free spirited one or even one build by the party's mage and serving them. I played a character's Butler once in a short-lived Space 1889 game, that was fun).
In 3E and later editions, the obvious choice would be Warforged. But with or without the Warforged as an easy-to-use race template for the idea of "i want to play a golem", you wouldn't need to write in an entire new species with an elaborate back-story. You don't even need Wizards creating Golems as a regular occurence. It could be just a one-time thing, one Wizard (or devil, or fey, or engineer, god or alien from outer space) making an experiment / dropping some gear.
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Also remember, one of the original things that started this discussion wasn't even tortles. It was taking away stuff from the PHB of the edition for your campaign. So something like "no Orcs" or "no Rangers". Which is something that happened during the AD&D era settings, where simply options were removed and billed as a campaign feature.
I liked Remalithis stance of asking: Okay, you want to take something away - but what do you add as options? If your setting is so much more focused that it can't be distracted by Warforged or Tortles or Elves or Sorcerors, how does this narrow focus manifest on the player side?
If your Sword & Sorcery game must go without spellcasting classes, what do you add to appeal to players that still like some sort of magic, or maybe you convinced them that they can do without, but they feel like the variations between the classes and within the classes aren't sufficient to them, and the game lacks complexity?