FCs have too much drama, which is why not everyone wants to join, even for buffs.

I got through Garuda EM on DF, but it wasn't fun anymore starting with Titan HM due to the high failure rate combined with the high amount of raging and quitting on first wipe.

I agree with others that PFs help increase what you can do without an FC, although you have to look a bit (or make your own group) to find one that isn't "i90 required for Sastasha, experienced only, no melee".