https://github.com/quodlibet/quodlibet is sometimes mentioned as a cross-platform foobar2000-like

Same for me when I was moving to Linux; missing a music player as good as foobar2000 kept me from changing for quite some time. In the end I settled with Clementine which is pretty good, but my music listening actually decreased quite a bit because of the change, strange as it may sound.

Not nearly as customizable as Foobar, but in case you're wondering if there's something better than iTunes, then Swinsian is a fantastic alternative macOS music player: http://swinsian.com/