Gaming aside (though that particular gap is beginning to close) I honestly can't think of anything I've wanted to do with my various Macs over the years that I couldn't because of macOS.

The closest I can get to is running radio station playout software, but that was less something I needed to do, and more an itch I fancied scratching at that moment. Other than that, my Macs have always had a way to do exactly what I wanted with them.