I realize this is an old post but I too ran into this problem and I while I was not able to get either of the "bind:Esri:fieldAlias" or "export to fgdb" workarounds to work for me, I did find that "export to shapefile" worked (from which you can then export to CSV from ArcMap/ArcPro). I do find it curious though that if you "export to CSV" directly from AGOL then the display names (labels) get exported and not the field names.