Well if the games aren't going to attempt to fit the game in the same universe why even bother calling it Fallout 3?
They do as much as they could, with the sloppiness of the previous games in the series.
FO1 and 2, hold a near and dear place in my heart. They are also, good games in their own right, but they aren't a perfect game. They had lots and lots and lots and lots and lots and lots and lots and lots and lots and lots of flaws. So many flaws that audiences of today, wouldn't stand for. And lets not forget the Bugs, so many bugs, lots and lots and lots ... of bugs and typos. So many that the game, would be decried instantly.
FO1 and 2 couldn't really decide if on its Tone or its Theme. Just an arbitrary starting point. Pretty much every facet of the game, is either broken, or incomplete. Its own story from the original two games barely make any sense. Srsly, you can defeat the last boss in FO2 with your severed mutated big toe. But hey, lets talk about creepy Vault Socio experiments because we're super cereal sci fi, oh wait, there Dr. Who telephone box. What time period is FO1 and 2 really a parody of anyway? You can't quite nail that down either... Oh sure, its lore has nailed it down, but what presented in FO1 and FO 2 is nebulous.
Oh man, did I get stuck in the conversation loop and end up having to buy Sullik again, even though hes in my Party. Whats that Sullik your Daughter/Sister is captured? That sounds like a great sub plot... oh its not in the game. Well lets just go explore FO San Fransico... oh most of the content was cut from here too.
But hey, that game world is bigger then FO3 and FO:NV, wait its not... if you actually consider the area you actually walk around your characters on then FO1 and FO2 game world, are extraordinarily tiny. They dont even really qualify as an open world. Especially not with games like Elder Scrolls 3. But hey, FO1 and 2 has a car! That you dont do really do anything with at all! You just got kinda faster on the very plain, barely detailed overworld map. At least Final Fantasy games on the Consoles, were using the fancy Mode 7, to give its overview world some interesting character, and AND it let you drive the fucking air ship. Not with Fo1 and 2, just a fucking dot, that moved faster. That car was fucking magical too, it went over all the terrains. Is that a crappy (even in its time) depiction of mountains? Fuck it. I'm a car that sits very low to the ground. I can handle those off road conditions, even though my car was meant for city driving.
Oh man, what about that the exact same linear progression of character items for both games? Sticking with the 10mm Sub Machine gun, until you get the Plasma Cannon, then do the upgrade for the Plasma Cannon and somewhere there get the Power Armor too and get the upgrade for that as well. Oh sure, the Power Armor, is super fucking rare, and only the Brother Hood of Steel, knows its actual working but those vendors in tents totes know how to a chemical treatment to improve the armor... somehow. Sure you can use different weapons, but you use different weapons not because the game is actually designed for it, but because you get tired of playing the optimal path.
Its really hard to have a focus conversation on the mountain of flaws and bugs in F01&2, as its so vast.
And talking about making game based on that? And to modernized it? How? The game is sooo disjointed, that any direction would be alien to the series and therefore make it in some respect dissimilar to FO 1 and 2. Giving the game, any grounding, any direction, any consistent theme or tone would make it dissimilar to the series.