IMO the issue is that we used his convention even after we realized he was wrong.
As a student, this trips me up immeasurably, especially after learning non-symmetric circuits.
We did so because it would have been even more confusing if one day we just switched the meaning. Electricity had been studied for a hundred years by the time we understood electrons as the charge carrier. In the mean time, many formulas were derived and books were written. To flip the meaning of everything would result in mass confusion about which way we were defining current flow. To disambiguate, we would want some unique name to describe one system versus the other. And so we did: we understand a distinction between conventional current flow and electron flow.
