It is fair to not want to do in-depth culture for all of those. However, there's an easy fix for that, which has been said multiple times before in this thread. Just have them be completely unique to the setting. The Tabaxi character was a wizard's experiment on combining a cat and a person. The Tortle was a turtle/tortoise that walked into toxic waste (Demon Ichor). The Tiefling was produced by their personal meddling with devils, infusing themselves with demonic essence.
Unique people can exist in the world.
Yeah, but there's a dynamic where that ends up making everyone prone to doing that, and bluntly, it can be hard to put things together for a party that stands out as a freakshow and not acknowledge that's what it is; and doing so can distort the game in non-trivial ways.
I know not everyone cares about that sort of thing, but not everyone runs a game to have every PC be a special case; 13th Age's dynamic here is not what everyone is looking for.