Yes, I'm agreeing with you. My point is that most people who think "paypal is doomed" probably don't understand the business with any degree of sophistication. Paypal has spent the last decade wriggling into every corner of the global economy, that's not something you can replace with some clever ruby code.
Which is why, despite its formal awkwardness, we have the option of the indefinite personal pronoun "one":
"If one thinks the the primary problem in payments is technical [one is mastaken]".
Personally I prefer the less formal compromise of "someone" (or "somebody", "anyone", "anybody" etc. with the choice depending on context and meaning):
""If anyone thinks the the primary problem in payments is technical [they are mistaken]".
Deserved because of the typo? One probably shouldn't make such mistakes when discussing grammar!
I suspect though that most down-voted before fully reading and comprehending that in my comment I said exactly what you just repeated - that "one" is correct, but stuffy, and that there are other, better alternatives to "you" when referring to a broader readership.