It's exactly the high-performance native extensions that require the GIL removal to allow for a full utilization of the machine. Although already successful as glue for these libraries, Python is ultimately hamstrung by the GIL on many-core machines. Using the GIL removal to start writing algorithms in interpreted Python is not the intention.
I warmly recommend reading the motivation section of the PEP. It is incredibly well written, quoting issues from PyTorch, scikit and NumPy: