depends
I still manage, but time is catching up with my eyes. Blade and notch sights, especially on a short barrel rig like an AK, give me fits. Shot a buddy's CZ trainer yesterday with 22" bbl and blade/notch sights I did OK at 25-50 yds, do to the longer sight radius. I can still shoot a peep well if the barrel is longer than 16-18", ie Garand, M1A, OK...M4 not so good. I still manage my agency qualification w/o trouble, but the post on the carbine is pretty fuzzy these days.
How good? I have a 6" gong at the corner of my place, about 120 yds from the side door. Bamaboy and I shot at it steadily all summer with an old .22 Mossberg M-44 trainer. Rifle zeroed "on" at that distance. Bulk of the shooting was seated w/ sling. I shot about 60-70% on it. We didn't keep notes, but that is our recollection (I just asked him).
Seems like I read somewhere that a "rifleman" should be able to go 4MOA with iron sights. I'm likely a bit over "par". I have declared this year the "year of the iron sights" and to date, have not carried a rifle deer hunting wearing a scope. I have not killed a deer yet either!..........but have not had a shot. Figured I better do it for my eyes get any older. You sure lose a lot of hunting time in the evening w/no scope!!!
I agree that iron / peep sights are a fadiing skill. Heck there are guys in my deer lease that have NEVER shot a rifle with iron sights!!!!! By all means, learn to shoot irons. Likely will help with your handgun shooting too!