Let me explain by example with Fallout 2.
I loaded up the game, made a melee/brute force character, and hopped in to the Temple of Trials. All pretty good as I went through it, despite the less than enthralling movement and combat systems, I was still getting into the concept of being a tribal trying to prove myself. Afterwards I was given the mission to go to Klamath to retrieve the GECK for my village, so I use the intuitive travel system to go to Klamath, here's where the game falls apart for me.
I go around the entire settlement looking for someone who knowswhere the GECK is. Noone had told me who to talk to about this, and noone in Klamath was giving me any sort of answer. In fact, I was becoming frustrated with the NPC's, who would make jokes about how the Garden of Eden was being in the arms of a prosttute, or that they've only ever heard of Geckos. I had no idea what to do, and I didn't want to look at any sort of walkthrough, because, for me, Fallout 2 is the type of game where the fun is in figuring stuff out. Looking up just what to do online would be like looking up the solution to all the puzzles in a Sam & Max game. What would the point be? But in the end I had to, because there was no way I was figuring this on my own.
Correct me if I'm wrong, but it seemed that the idea behind Fallout 2 is that I am just supposed to drift around doing side quests until by chance my adventure leads me to the location of the GECK that my village so desperately needs. I don't understand this. It's even worse in Fallout 1, where there is a time limit. Not only that, but at first the game seems like it's going to be fair and give you some inkling of what to do by sending you to Vault 15 to get the Water Chip. I went to Vault 15 and found out that the area meant to hold the chip was blocked off. This is after having bought 2 sets of rope and clearing the entire vault looking for the chip. I sulked back to Shady Sands, where people had no idea where the chip would be either, they just wanted me to kill radscorpions and raiders. I had a Vault to save, goddammit, I didn't have time to play courier for a bunch of traders.
That's my two cents, I just couldn't play Fallout 1 and 2. I wanted to go from place to place, doing what I have to do to save my home, but instead I ended up aimlessly wandering, desperately looking for some quest that would lead me to salvation.