That said, given the stats I agree with their prioritization. OSX makes up 1.39% of their market share: https://store.steampowered.com/hwsurvey/Steam-Hardware-Softw...
Linux has a higher market share than OSX (likely due to the Steam deck, but still I was surprised by this).
I actually think this is something Apple should be taking the lead on, rather than Steam. It's clear that they value gaming on their devices, they just invest so little in it. Input latency is still poor and there are still big hiccups in frame rates which make competitive games on OSX a non-starter. If Apple invested more here and partnered with Steam, they could make some significant headways. Apple seems to want to avoid partnership here though (ie the prior vulkan vs metal issues).