There's a bit of nuance to THAC0. If you've never heard of it, you're young. If you know what it stands for, you're starting to get old. If you know how it works, you're old. If it's the right way to play, you're d u s t y
THAC0 is just subtraction instead of addition. I'll never understand the hate it got.
I have no problem with ascending armor classes and attack bonus. The math is the same. It's easy and intuitive. But if you're having issues subtracting whole numbers less than 20, you've got a problem bigger than the wrong game system.
I stopped paying attention to D&D (though not RPGs!) long before whatever schism you are referencing occurred. It's awful. But I know what I need to roll to hit armor class zero.