Steam getting a 30% cut is certainly less objectional that Apple getting 30% because they've locked other people out of selling on iPhones.
On the other hand, that Steam taking as big a cut as Apple can claim because of their unfortunate practices isn't great.
Generally, the smallest indie creators, who aren't really likely to benefit from organic discovery on Steam, seem to priority selling on itch, which, by default, only takes a 10%, despite doing all the work you mention.
That Steam seems to have a marketplace monopoly based on network effects, and this allows them to claw money from all but the largest and smallest game developers is not something they have a strong right to claim to morally, and something society would benefit from doing away with. It appears that 72% of game devs feel that way too.
So, to answer your question, for me, two thirds of Steam's revenue seem unfair.
On the other hand, that Steam taking as big a cut as Apple can claim because of their unfortunate practices isn't great.
Generally, the smallest indie creators, who aren't really likely to benefit from organic discovery on Steam, seem to priority selling on itch, which, by default, only takes a 10%, despite doing all the work you mention.
That Steam seems to have a marketplace monopoly based on network effects, and this allows them to claw money from all but the largest and smallest game developers is not something they have a strong right to claim to morally, and something society would benefit from doing away with. It appears that 72% of game devs feel that way too.
So, to answer your question, for me, two thirds of Steam's revenue seem unfair.