The GIL is a good decision and has been a sound engineering tradeoff for decades. It's only been the past few years that running the interpreter without a GIL has been even remotely feasible (cf the gilectomy project). The GIL is a relatively straightforward way to hold back a tremendous amount of complexity.

Similarly, TOML writing is a ton of completely. The org isn't opposed to adding toml writing to the stdlib fundamentally, they just aren't rushing and want to hammer out all of the grossness first.