#1 thing for me would be the soundtrack. The Trial themes throughout FFXIV have been some of my favorite pieces, and EW did not disappoint. And with the xpac being the one to "wrap up" the current storyline, I particularly loved how the final trial incorporated motifs from several different xpacs along the way, building to an EW theme.

#2 would be Elpis and the final zone. I loved the storyline in both, and the going back to the musical theme, the way the music was used in the final zone was awesome to me.

#3 would be the callbacks, both to other FF games and earlier parts of FFXIV. In particular, FFIV is my second favorite non-MMO game in the series, and I enjoyed seeing it at last get big references in FFXIV. The final trial phase transition in particular gave me major vibes of one of my favorite moments in the entire FF series. And I really like how even some of the random side-quests incorporate past events. Discovering/realizing what happened to Tataru's carbuncle from soooo long ago, meeting a certain relative of a certain Scion in Sharlayan, etc.. I love how they manage to bring back things from the past in ways that always surprise me and make me smile (or tear up, as the case may be).