How come there are few freshly built civilisations (new houses etc) in newer Fallouts when it's been 200+ years since the Great War? Why is rubble still everywhere?

Both the West and East Coast have their own justification on their state of being; one is relatively left unscathed while the latter is bombarded into pieces. One of the superficial examples of this matter comes from the accounts from Mr. House and Carol, they pretty much explain the aftermath of the Great War in their space.

And it's a bit of a misnomer to assume progress omnipresent, or at least how you define. The West Coast still has some "primitive" folks scattered throughout, especially East of the Colorado River. And it would've been boring every inch of land "civilized" to the point discarding one of the most important piece in the series - the sense of adventure.