Yes, how dare the game have a plot. How DARE it! They're ruining storytelling forever, by inflicting this STORY on us!!?!? 
/sarcasm
Also, you seem to be wandering between topics - you start the thread wondering if the optional "build a settlement" module of the game means that it's The Sims. But you seem to have slid over to the good old "they're constraining my character too much with their plot, roleplay ruined!" topic instead.
edit: so did the addition of fully-romanceable-companion mods or the Real Time Settler mod to Fallout 3, make it "no longer an RPG"?
edit2: it's also interesting to contrast "is it turning into a life sim instead of an RPG" with the people saying how life-sim features (like needing to sleep/drink/eat) aid their roleplaying. Or the people who talk about roleplaying "mundane" characters & jobs - like a town guard..... you know, simulating a life.