I haven't looked into this deeply; but for several years now Jen Simmons has been posting stats in which Safari is either the top scorer for interop, or is very close to the top. For example: https://front-end.social/@jensimmons/115749303356986835

I do not know enough to tell whether this means that modern Safari has finally stopped being the new IE6, or that she is just doing marketing that misleadingly focuses on some features, while other, more frustrating and more deeply rooted, issues remain.