Well I don’t know much about weaponry, but it does seem like Lebanon sends a billion rockets a year into Israel without killing a soul the vast majority of the time (Thank God).
How accurate are missiles lobbed from less than cutting edge tech countries?
Again, I have NO IDEA.
Can they just suck at being accurate?
Yes, unguided ballistic missiles are that inaccruate. They are area weapons; meaning you are aiming them at a point on the map and they will land within a somewhat-predictable area. Hitting a specific point target is either a matter of coincidence or saturation. When the US introduced modern guided munitions during the First Gulf War it was a complete game changer, and we've led the way in their development since.
The German V-2 had a ballistic accuracy of about 10 miles. A 200 mile range with an error of 5%. Launched from France, it might hit London. They fired dozens at the Remagen Bridge, without effect.
The Iranian ballistic missile could actually be that ineffective.