3. Task resolution. Good heavens, this is quick. You’re an elf and want to listen at a door? Roll a d6, you have a 2 in 6 chance of success.
For a different perspective, and one view on where I suspect many part ways with the old school mentality:
What I always found with this, when those old-school versions were all there was as far as D&D was concerned, was that what you write here
seemed true when you were looking at one class or one mechanic. But because there was no consistency to which dice you rolled or which numbers you needed or even whether you wanted to roll high or low, I could never keep these mechanics straight, even if
individually they were very simple.
(I don't know if this is as true in OSE, but it's pretty true in the version of the game it emulates.)
I don't see what's harder about "roll a d20, add a number that
should be written on your character sheet, does it meet the target number?" except in cases where that "should" isn't met. Which I get if you're playing with, like, very young kids, but otherwise that's a player problem. Plus it lets you vary the difficulty. Why would every secret door be equally difficult to find? I'm not necessarily convinced that d20-plus-modifiers was the ideal choice, but give me
some kind of unified, scalable mechanic any day of the week.