THAC0 didn't come around until 2e, 1e had hit tables. You can see them on p. 74 of the AD&D DMG, with some more notes on p. 82.

You can get rid of THAC0 if you just use this simple rule: roll d20, add the opponent's armor class (plus your own to-hit bonus if any), and a result of 20 or better is a hit.

That's true; it's easy to forget that THAC0 was a simplification from 1e.

Though that kind of reinforces the point.

Yea the salient point there was the second part - whether it be hit tables or THAC0, 5e rules would expedite play.

Course some of us will sit there and say y'all should just be playing 3d6 instead, but I digress...

Actually it was introduced before 2e but wasn't a core system in 1e.

I don’t know editions subsequent to 2e, but I kind of liked THAC0. Tough to explain, but flexible. A useful abstraction.

3E's Base Attack Bonus was mechanically identical, but expressed in an easier-to-understand way. Briefly, they rearranged things so that higher numbers are always better--having +1 armor no longer means you subtract 1 from your Armor class.