I hunt with both open sights and optics. Love them both. I have an old marlin 39A with open sights as well as two CZ 455 trainers and a Win 75T with aperture sights. I find shooting something like rabbits with them much more effective with fast target acquisition. It is easier to get tight groups from a scope
on a bench, but if shooting freehand I believe that the lighter and better balanced rifles with open sights can group better. I do three things to facilitate shooting with open sights.
First, I always keep both eyes open and on the target. That helps with fast target acquisition and gives better depth perception.
Second, you need to make sure that your rifle fits well - shoulder placement, cheek weld, etc so that when you bring your rifle up it is on target and the rear and front sights are in proper alignment.
Third, if your gun fits properly and your sights are in alignment, then only focus on your front sight and your target. This helps with old eyes and focus. Trying to line up the rear sight and focus on it, your front sight and your target is just too much for even many young eyes.
If I am out in the field using open sights, I can usually out shoot others (and myself) who are using optics when shooting targets of reasonable size - this may be 4-6 inch targets out to 100+ yards. Shooting small targets like a ground squirrels head poking out of a hole is better done with a scope.