I've never had a FR RPG experience, and nothing I know about it makes me wish it were otherwise! What you say here is pretty consistent with my impression - I don't get what makes it so popular.
I think a lot of it comes down to mistaking quantity for quality. There is so much material out there for the Realms, it must be awesome!
The Realms can be good, but it takes a solid and creative DM to manage it. Do you use
all the existing Lore? Do you retcon stuff? Do you change locations, NPCs, etc? It can be a lot more work to undo all of that "worldbuilding" and clean out the kitchen sink than to do your own homebrew and pull elements, locations, adventures into it.
Another plus for some DMs, and particularly new DMs, are the adventure paths that go from Level 1 to 15 or what have you. Its a self contained campaign that can run for as long as it takes, you only have to engage with what is in the adventure, and while some have some dubious quality/internal consistency, a new DM can rock that in the Realms, and be good to go.
Compare where FR is now to both the Forgotten Realms Grey Box, and the original Greyhawk Box. They're both expansive, but only give very broad brushstrokes about what is going on in the Realms and Greyhawk. Its up to the DM to build the larger worldwide goings on, add in adventures, details, etc. Now, a DM can certainly remove large amounts of FR lore that has built up, but that can be challenging in itself (and I've done/tried that). My Greyhawk campaign, even though I'm using From the Ashes, is still fairly "open" in terms of the impact of the wars outside of what is in the Ashes Box set. I'm not familiar with, and won't seek out other lore, and its also not as pervasive. My players certainly don't have any idea of what else is out there. So it helps focus my worldbuilding.
There are also a lot of novels, modules, etc. that have been produced, which many people (including myself) devoured. Lots of cool imagery, locations, adventures being had, and then as a player you want to replicate those, or visit those locations in-game. And I think, finally, there is a comfort in "kitchen sink" settings where, as a player, I can do and be whatever I want. I can play any race, any class, worship anything, and no one in-game will blink an eye. And there is nothing wrong with that, its just not how I and my players engage with the settings at our table. I mean, there are only so many times the world can have spell-something catastrophes, a toss around of hundreds of gods, world-shattering events, cities being pulled into hell, hell opening up onto the sword coast, Tiamat/Dragon cults doing something
again, whatever.
And none of the above is to say that one way to play is better than the other, or anyone is playing wrong, etc. I can understand why the Realms is so popular, its got a ton behind it. I have played it, and DM'd it, and don't find it as engaging as I did before.
