It's kind of a running gag that XIV has more endgame variety than most games have hours, but there is some truth to that, depending on how you want to define endgame.
'Hardcore' would be going through relic grinds like Eureka or Bozja, which, for clarities sake, is essentially old school MMO 'kill shit to level up, don't die' style...It *is* instanced, but not like a dungeon. More like a mini-world map. There's also treasure maps, which are mini-dungeons that only proceed based on luck, but give big rewards (due to the music, sometimes called 'funky casinos'), plenty of post game questlines, like Hildibrand (Comedy questline that varies between cringe your soul out to genuinely well told and touching. Depends on your tolerance for hijinks.) beast tribes (give tiny quests, 3 a day, for more insight on the other inferior races), custom deliveries (crafting challenges), Blue Mage (somewhat boring 'limited class' that can become laughably OP, but is not allowed in any real instanced duties), hunts, fates, and a shit ton more I can't think of.
'Casual' would be shit like gold saucer, which includes triple triad (the card game) chocobo breeding and racing, minigames about dodging mechanics, Prince of Vermillion (a jank ass psudo RTS where you use your minions instead of troops), and the weekly fashion report, where you try to impress an NPC with your fashion by trying to decipher his awful hints, before going to the reddit and just buying whatever they find. There's also now the Island Sanctuary, which is an instanced, super chill 'fuck around and vibe' area, and of course, ocean fishing, which actually makes fishing somewhat enjoyable to level. There's also jumping puzzles scattered around, and vistas to fill out.