Since you wanna use words like ethically when talking about a computer game and stuff, i'll say this. Saying, "That discrimination is "If you don't have a E/R/M, players just DON'T want you to join in their events."" is the same as me saying "i don't want a surgeon without a medical licence".

Some events need DDs to do enough dmg and if you haven't got a r/m/e you need peoples respect to show you can do good DMG.

Some DDs need an emp like MNK and WAR so if ya wanna do endgame w/ those jobs u need to get an emp or just don't do endgame.

Others can do decent DMG without E/M/R like DRK and SAM but without those like i said you'll need to gain some respect with people you play with regularly (as a linkshell or friend list works) or people would rather /trust a DD with a relic.

If this is an issue to you just play a mage or learn to lead.