Fallout 3 is an open-world game, but it ends. Fallout: New Vegas is an open-world game, but it has direction and pacing and writing and it ends a hell of a lot stronger than most any other game I've played in recent memory.
Fallout 4 seems like a number of smaller games with a loose goal. But screw that goal if you want to play Fallout: The Sims, and by the time you get to the main city you're pretty unrestricted as to where you can survive, unlike FO:NV which if you tried to wander off said, "Hahahahahaha did you want to not be dead because too bad, now you're dead!"
That is, in FO4 and FO:NV, it's open-world but you are directed. FO4 pushes a moral urgency on you from word go (which is fine) then doesn't give a damn about that urgency until a mid-game boss-fight and the end.
Someone once complained in my presence that Fallout was a bad game because your stats dictate your combat skill. Had they not been a terrible troll who would say things like that just to say them, I would have said, "It's an RPG. This is what RPGs do." They force you to act within a series of rules and roles, and this is something that Fallout 4 mainly fails to do.
Incidentally, other little things I liked better in FO:NV, besides a story: Wear and tear on things. Power was explained or nonexistent (screw you working terminals and elevators and lights for no reason, not to mention ever-burning candles). The radiation system (the new one su-uuuuuucks). I think I preferred how rare finding a safe place to sleep was, and in fact scarcity exists barely at all in FO4. I want to like that we have a solid history that leads up to the Fallout world but why was everyone in 2077 still in 1950s styles?
I feel like Fallout 4 had a ton of creativity poured into it but it didn't go far enough. It's the usual list of Super Mutants, Ghouls, and Brotherhood of Steel. This is partially also a complaint of FO3, but they had a chance to branch out here ... and missed.
I liked the game. I liked it a lot. Just ... I don't want this to be what people think Fallout is at its best. It's not.