My old boss kept a set of 90s blueprints rolled up in the corner as a joke. The line weights were so faint you needed a magnifying glass just to see the property line. It wasn't just about better pens, the whole mindset shifted from just getting it done to making it actually readable for the guys in the field.
Honestly, that take feels a bit off to me. I've seen plenty of old timers who took real pride in their draftsmanship, even with the tools they had. The faded stuff usually came from cheap copies or guys who just didn't care, not the whole era. Tbh, the real shift was just having computers to fix mistakes easily instead of starting a whole sheet over.