^^This is one of the several reasons I re-encode Ren'Py and RPGM assets to lossy formats. Some of our members literally cannot download the full sized games. Thank you for this, it is noticed and appreciated.
Since Unity games store all their assets uncompressed in their own proprietary format, I can't use lossy re-encoding. But I do repack them with 7zip all the time with very good results. You probably know this already, so stating more for other's benefit.
FYI - while there isn't an actual 7zip client for Mac, there are clients that support it. Keka, the Unarchiver, and Bandizip.
@goobdoob - what do you use for 7z files on Mac (I don't actually own one).
And in case you care, here's the settings I use for 7zip that work best in my experience.