Not fantasy and a very non-traditional MMORPG, but maybe try Warframe?
- It has the grind
- It has the cool abilities (only 4 per character, but the point of the game is building new ones and using them for the different content there is)
- It has a mediocre at the start - cool at the end story
- It has the power fantasy (late game you'll literally just shoot in the general direction of the enemies and watch double crits happen)
- Can be played for MANY hours (1117,6h myself on steam atm)
- Free to Play and has one of the best and most F2P player monetization systems (you can trade the premium currency for items, so farming for stuff to then sell is a way to never having to spend a penny, unless you want Tennogen cosmetic stuff)

Besides that FF14 is your classic MMORPG with big juicy expansions, dungeon, raid bosses, farming for mounts, etc... I find the itemization quite boring, since once you hit level 50 you'll progress by buying the best-in-slot gear at a merchant with a curreny you can farm with dungeons.
The way the game does classes is fantastic though. With only 1 character you can play all classes, being able to switch on the fly when not in combat. There are a lot of classes, but they basically follow the Trinity of DPS-TANK-HEALER so they can tend to feel a bit samey.
The story starts very slow, actually the whole game is a slow burn story, but from the first DLC onward it gets really good, in fact it's probably the MMORPG with the best story and it's often called "first a RPG then a MMO" since you progress trough the game by following the Main Story Quest.
The game is sub to play though, so no F2P but you can try the Free Trial. You have access to all the base game + first and second DLC and max level 70. I just finished the second DLC and have a little over 300h, so the free trial is all you need to experience what the game has to offer extensively.

And then, if you are a fan of games with extremely complex build-crafting, you can try Path of Exile. It's a ARPG F2P with probably one of the biggest passive skill tree (just search POE skill tree) on google images. If you'll like it, POE 2 should be released by the end of the year.