Quests. I never was, and likely will never be, too much for random pointless exploring. A dungeon dive every now and then is fine and even fun at times, but it shouldn't be the crux of the game (a hasty story thrown amidst of a landscape with huge amount of temeparkesque set up of random dungeons, as I viewed Fallout 3). New Vegas, imo, had the right idea by connecting much of the exploring to quests - that gave an incentive to scourge the map a bit as my scourging had a purpose other than pointless loothoarding. Could it have been better? Sure, but in my eyes the "exploration" aspect of New Vegas was already better than that of Fallout 3 (and I do count finding the differing outcomes of the quests as part of exploring). The characters and setting were more interesting and felt less "tacked on" (to me), which made wandering around and looking for places more worthwhile and intriguing. Imo.
actually a sandbox games need what you call "pointless" exploration... fallout is a post apocalyptic franchise and whether everyone likes exploring or not, "realisticly" in a post nuke world you would be exploring, scavenging and fighting enemies. but aside from all that, just leaving a huge open world barren and desolate and just throwing up tents and one room shacks all over most of the map is just a lack of serious thought and development, its just a cheap easy way making a game, with no attention to the real elements of a post apocalyptic game, the story alone isn't that great and even it is lacking suspense, drama and action, so to me its just a game thats incomplete, not well enough thought out, rushed and with a lot of misplaced priorities.