Accuracy isn't just your bonus to attacks, it is your bonus to attack in proportion to the AC you're trying to hit.
AD&D runs the gambit, beginning around 30-35% accuracy and culminating around 60-70% (or better, in Monty Haul games).
5E begins at 65% accuracy in typical cases, and stays around there for the most part to level 20.
In 5E, you are more likely to hit than you were in AD&D. So, 5E has better accuracy.

I'm not saying the "bonus" is higher in 5E vs. AD&D (although at low to mid levels it does), I'm talking about actual accuracy.
Now, if you want to discuss the ballooning of accuracy, then yes,
in that sense AD&D improves much more, but it also started out at half that of 5E when it comes to accuracy. 5E doesn't balloon accuracy (as we know), it ballons hit points and damage (although less than hit points) as yourself and many of the rest of us have already acknowledged.