Okay, I'll bite.
Pick your favorite pre-5e edition of D&D and without looking at a book, tell me:
* what is the penalty for fighting a prone target?
* what is the bonus for having higher ground in melee?
* what is the penalty for fighting blind?
* what is the bonus for flanking?
* what is the penalty for using an axe underwater?
And is it easier to remember those modifiers than to assign dis/advantage?
Ah, you have me at a disadvantage

As I have multiple-edition personality disorder.
1. +4 to hit vs. prone
2. +1 or 2. Depends on circumstance - grade, weapon length, time of day...
3. That's always been a -4 as far as I recall.
4. I don't use minis. Probably a +1 or 2, - shield depending on side
5. Hmm. Good one! I'd say -3 to hit and 1/2 damage. Better take a trident next time...
Thanks for "biting", I think I'd reverse my previous statement: advantage makes the simplest base mechanic for any such situation - but - knowledge of previous editions can add variety and perhaps verisimilitude, and on the fly rulings can increase the granularity (sun in our face attacking uphill on a steep grade w sword while opponents have spears, whathaveyou...)
having finally read the Basic rules pdf, I am really happy with what I see. Seems a versatile base.
Cheers, and good adventuring....