It's primary usage is likely to be when you already have a dedication, but not it's follow-up 2. You can then ignore the need for other feats before taking that one, but would still have to fill out the necessary requirements from there to take any others.
For instance, in my attempt to recreate a mystic theurge (only BETTER), I was going to be going through multiple caster dedications with all of my class feats (except 6th because of level requirement shenanigans). If I didn't pick up the Breadth feat before level 9 then I wouldn't have enough to take the new dedication, but with the Multitalented feat I could.
That would not however allow me to pick up another dedication until I had fulfilled all of my requirements for the others, save for using another ancestry feat for Multitalented again which, correct me if I'm wrong, I don't think you can do.