I was just noticing -- other than the most savage people in the commonwealth, or those wearing heavy armor rather than clothes, everyone is wearing 200 year old clothes. Pretty much everyone. In New Vegas, you had a lot of people wearing non-armor clothes that conceivably were made post-war. I don't remember the names of the outfits but I remember seeing them.
I have a pair of jeans that are years old but are on their last leg, going to have to be retired.
I've realized that if I could wave my hand and change things, I'd put a lot of them in post-war clothes of some kind, even if those clothes had a semi-pre war aesthetic.

There are a few outfits that look like they were made post war like the brahmin skin or wasteland settler outfits but they are certainly in the minority. Fallout certainly does have a lot of logical inconsistencies, like how do the guns still fire after 200 years? I just see it as artistic license.

Though it's often a criticism of fallout 4, the gun selection is a little limited, and many of them look nothing like any previous fallout weapons. Leads me to suspect that maybe so many of them are post-war designs (and not just the pipe guns.)
The gun selection in mods like New Vegas classic fallout weapons is quite nice, making me wonder why devs don't just use the old weapon lists. Nothing wrong with that extensive list of past fallout weapons. But yeah, post-war designs, a lot of them, I think.

I don't think it's that inconceivable that the clothes made are post war. It's really not that hard to stitch together a shirt, or even a suit if you have the time and patience. This is the same game that lets you build nuclear reactors and super computers out of scrap metal, and so clothes really aren't that big a deal. I didn't play much of 4 though, so I'm not sure if they explicitly said the clothes are pre-war.