It seems to me that some older cards would have worked better as events, e. g. Chancellor, Feast, Navigator (which already has an equivalent in Scouting Party) or Saboteur. If you had included events in every Dominion set starting with Base, would you have used their effects in events instead of cards?
In this alternate universe, do I also know how things turn out? I mean uh. I wouldn't make Feast today, but I did back then, and was happy with it. I wouldn't have been thinking, "oh man maybe there's some different way to do this." In fact a lot of questions along the lines of "why did this early card do things this way" are answered "that was what I started with and I never felt a need to change it." If I'd had Events early maybe I would have saved them for one set's thing; if I decided to put them in every set, they'd be whatever other effects, they wouldn't replace existing cards, which as far as I knew were already doing good work I had no reason to throw away.
Instead we can consider, what would I do now, knowing how things turned out. Here though one thing is that I don't have any special need for a particular card to exist; I don't need Event-style Feast, I can just not do Feast. Maybe some bad cards work well as somewhat-related Events; it would be a case-by-case thing that I sure don't need to work out in this thread, if I ever want to do them.
And there's that: if Event-style Feast is cool then it's still on the table now, nothing's stopping me.