You are going to have to explain this. They are barely different to me.
As I understand it, the old cheeseburgers fried the meat on the fryer, and then added toppings at the assembly stage (cheese, ketchup, mustard, pickles, and raw diced onions).
McDonalds decided to "boost the flavor" of their burger (apparently in response to the popularity of the new Beyond Meat burgers) by putting the diced onions directly on the grill, and then dropping the uncooked patty on top of the onions to let it fry that way. Instead of just frying the patty, the patty gets intermixed with sauteed onion.
I've basically never met a cheeseburger I didn't like. I could tell that the McDonalds cheeseburger was a low quality burger, but it was simple and enjoyable. I really liked it.
When I first had one of the remastered cheeseburgers, I thought that someone seriously fucked something up. But that happens, whatever. Next time I had one, it was the same thing. I figured they had some sort of incompetent new chef, and was thinking of not frequenting that establishment anymore. Next time I had one at a different location, it was still terrible (IMO).
A little while after that, I saw that McDonalds was advertising their new "remastered" burgers.
I tried ordering one with no onions, and that was an improvement, but it's still being negatively affected, probably because McDonalds has melted onion all over their grill now. Don't want it? Can't escape it.
McDonalds had dropped from #1 in my burger consumption to somewhere between last place and total disqualification.