AD&D (1E or 2E) had typical AC's equivalent to 15 to 25 in terms of 5E. At higher levels, via magical items, you could easily have ACs down to -8 or lower (equal to AC 28+ in 5E). 5E does to this better than 3E certainly, and I expect better than 4E (which I never played).
Yes, AD&D, instead of resistance to non-magical weapons, had MANY monsters which required a +1 or better weapon to hit. They were invulnerable to anything else. Higher HD monsters could hit other monsters requiring a +1 or better weapon:
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So, an Ogre (a 4 + 1 or more HD creature), could hit and injure creatures which required a +1 or better weapon to hit.
However, the game was built on the assumption that PCs would have items of magical power roughly equal to +1 per 4 or 5 levels of the PC. So, if you have a 13th level Fighter, you probably had a +3 weapon as your major weapon, +2 or +3 armor, other items of equal or lesser power.