To me the main issue would be that an income tax prior to 1913 were temporary taxes. Technically, yes they were based on income. But when we talk about income taxes today, we don’t talk about them as necessary tools to generate revenue in support of a war that would have an end date.

It wasn’t a permanent fixture. Today it’s a permanent fixture and short of one of the Paul clan winning the office, it will continue into the foreseeable future.