we dont know when people started using caps. It could have started as an illegal currency and grown over time, and considering the game begins 5 years after they left, it is plausible.
It’s fallout 76 not economy simulator. If everyone was using different types of currency, what kind of an online game would that be. When you die you just reappear. This is how multiplayer games work.
The easiest fix to the currency issue though is for Fallout 76 to not be a MMO game that requires regular currency but that's not happening now, is it?
Also, genuinity? You'd reach for that excuse to justify some inconsistencies in a series with pretty well-established lore and history? If I wanted genuinity, I'd play an established MMO game with an established player base. Also, genuinity isn't a real word.
Also I never expect Bethesda to become competent. I express my snide remarks about their usual icompetence by framing them as a question. Whenever I do this think of RLM's Prometheus video.