RE the idea of a kitchen sink.
I don't see this as the opposite of a curated list of races/classes/other options. Ultimately, the game only has to have the things the players have chosen or are allowed to choose.
If one of my players says, I want to play a warforged, and we work it out in some way (either by adding the race to the setting, or by coming up with some unique origin for the character) that doesn't make it a kitchen sink.
The two things are not mutually exclusive. My list of allowable races could consist of the exact 4 races chosen by my players for their characters and no more.
For me, when I question such restrictions, it's not about the restrictions themselves, but the reasoning behind them, and how that compares to player desire and satisfaction.
If a character dies (or a new player joins, or they're tired of the old one) does the list stay at just stay at the four for the late addition?