I tried playing through Fallout 3 again recently myself. Just so I could point out to people why Fallout 3 is miles better than FO4, and I just couldn't do it. It really just felt like, unlike in New Vegas, my decisions didn't mean jack squat when it came to the world. Perfect example I can think of from that playthrough that made me quit:
So my character was always a fan of horror movie night in the vault. He loves everything scary and horrifying. So of course, he really really likes ghouls. So much so that when he finds out Roy and his friends aren't being let into Tenpenny Towers, he decides to help Roy out by following Roy's evil plan of letting the ghouls in to slaughter everyone.
So my character did just that. he managed to pickpocket the key to the room off of Gustavo and made his way down to the generator, opening it up for ghouls to flood the place. When he went upstairs with the ghoul mask, the whole place was in chaos. Bodies everywhere, people screaming bloody murder, guards shooting at ghouls desperately before dying, every door in the place broken wide open, all the electricity in the building shut off, it was so atmospheric. I absolutely loved it. I thought to myself: My God, this game actually has some fucking atmosphere!
And then.. I leave Tenpenny Towers to go pick up some supplies and let the ghouls move in. And when I come back? Everything's perfectly fine. All the doors are fixed, the electricity's back on, there's no bodies or gore anywhere, nothing's destroyed. Everything's back to the way it was with the exception of the hotel now being filled with nonferal ghouls instead of people. After only 2 in-game hours. Seeing the hotel go from a site of a massacre to being perfectly okay again broke any immersion I had, and I haven't played the game since. Yes, it was that bad.
Give it a try for yourself, you'll understand how fucking jarring it is. Terrible, just terrible. It was going so well too!