I still use open sights just about exclusively, at 70 years old and with corrective lenses. I have one, centerfire rifle with a scope on it just because I had the scope and that was the only rifle I had with bases and rings.

I can still shoot 2 inch groups with revolvers/pistols at 25 yards.
I can still shoot 1 inch groups with open sighted rifles at 50 yards. (just did, two days ago)
With aperture sights 2 inches at 100 yards is pretty normal.

All with accurate firearms, benched and bagged, obviously.

I haven't shot a big game animal with a scoped rifle in over 30 years.

When I can no longer see to use open sights, I'll go to a scope.