I'm an avid FR fag. I do recognize its downfalls. Power Creep (though Ed himself touched on this on the 3rd ed sourcebook, see On Concerns of The Mighty) of Marry sue heroes. Too many mediocre if not shitty novels
But I still love the FR the abundance of material, in vidya, in sourcebooks in novels makes me happy. I don't hate Greyhawk per se, and one might want to have a vagueish enviroment where the player and the dm fills the gap.Hell, Pathfinders Golarion is like that and thats one reason I don't like it. I think this is just a personal preference. But I do love how rich in material the FR is, I can pick a random spot on map and could mostly find an article on wizards 3rd ed archive about it at the very least. Usually I can find a sourcebook.
Greyhawk in 3rd ed was not supported fully, maybe that became detrimental. And I also hated how in 3rd ed every setting got its unique planes. I think this is reverted in 5e and I really hope all the old tsr settings make a come back, bound by an unified cosmology/planar system and if I may wish hard, spelljammer too.
I don't know, some people really hate FR. They hate the novels, they hate the powerfull npcs ( I mostly ignore them, then again this is might be ignoring the problem rather than solving it), they even hate the vidya. They hate how everyplace is mostly grounded in one way or another and DM's have little leeway to create their own stuff(which I disagree, but anyways). But I don't, even since I was a wee lad I liked FR, you can call me the infinitive engine generation, BG I-II started me on FR. Though it was not the first setting I knew, I had read a little bit of LotR, finished 2 books of Dragonlance but they never clicked with me. I hated dragonlance and just read it because everyone in my school was reading it (dragonlance was REALLY popular in my country back in early 2000s partly because it was the second translated novel after lotr). With FR something clicked I think its just a preference.