Oh and when I DM'd I just translated this for people. If the orc has an ac of -3 and you have a thac0 of 12 then you need a 15. So your roll plus modifiers. I guess the problem would come if someone always thought "I need to roll 12, right?"
And I agree advantage is sooo much easier for new players but it also sooo much more powerful than your standard buff and there so many ways to get advantage . . .
But anyway, the days of Thac0 are gone. (until WotC lets us have 2nd ed srd)
I think it really comes together for people when you tell them that the 'normal unmodified human' with his 10 in every attribute and no class always has 10 as their median, i.e. why base AC is 10, and why any check of 10 is 50/50 proposition for a regular person. This also comes into play with Attribute scores, the average Elf is always going to be more dexterous than their average human counterpart, so they start with whatever the "Vitruvian human' counterpart would get +2, because the Vitruvian Elf "Dex 10" is a human "Dex 12", this is what I think of when people get touchy about built-in racial modifiers.
