Yes, but Jython and IronPython (which were the only implementations that I know of that effectively didn't have a GIL) were much slower in general, didn't work

Yes, but Jython and IronPython (which were the only implementations that I know of that effectively didn't have a GIL) were much slower in general, didn't work with native extensions and were always lagging a lot on the supported version (so, yes, there's not much interest in having a GILless version with these shortcomings -- so, IMHO, CPython is right in only accepting a GIL removal if the performance in general doesn't suffer and which has a good path forward for compatibility of the existing native extensions ecosystem).