hi! few months late but i'm a mac player too and i found a way to make it work? you have to download the windows version and follow this reddit post https://www.reddit.com/r/RPGMaker/comments/186fmuh/guide_how_to_play_windows_rpg...
unfortunately i don't think save files work properly so you'll probably have to keep the tab open (haven't played much yet so idrk) idk if you're looking for a response but just wanted to share in case!!
edit: been playing around for a bit and i think i found how to make save files work: open developer tools on the browser you're using (f12) and find local storage (for firefox it was under storage), then copy the long text under the key "RPG file 1" (or whatever number) and you can paste it in again when you reopen the tab