I worked on a ton of stuff in the early 2000 timeframe that had the bad capacitors, it was a very common sight. I actually rescued a couple of computers with the bad caps, I just replaced all the electrolytic caps.
I think most everyone associated with electronics heard about the Capacitor Plague back then. Remember these sights?
Others will disagree, but I suspect that this is at least some of the reason that the old 5V boards have failed. I've noticed in particular one capacitor brand is frequently bulged and bad, WinCap.
I have at least a dozen dead boards with that cap leaking/bulged, all the WinCap brand. It's certainly not the only reason they fail, but I strongly suspect it's one of them.