The only ones mad are people like us who can't get this shit and want to buy in. Vocal minority of the Internet.
Exclusives have always gotten people in the door, and are always a strategy to get people to buy more. Imagine if 100 people walked in to try to find Rosalina, and of those 100, 50 bought a $2 drink. $100 in sales they wouldn't have had. Imagine mom sees this exclusive product in an ad and had to go shopping anyway, goes there and they're sold out so she gets Peach instead because her daughter likes both characters. She then spends $100 while there. 10 moms do that. That's $1000 that would be at another store!!! It's a known marketing strategy and always has been.
This problem hasn't even hit mainstream news yet on a large scale and likely won't. Grown men complaining about not being able to buy a toy isn't exactly a news story people care about :-\...
At the Target I went to on Rosalina launch day, there was a line of about 25-30 people. They ran out in minutes after the doors opened. There were about 15-20 people that didn't get a Rosalina. None bought a Peach instead, all were pissed off and left the store without buying anything else, cursing Target and Nintendo. Some did have other items they had wanted to purchase, but put them on a shelf as they were walking out.
I don't know about any marketing strategies, but I do know most marketing is a load of BS and lies designed to convince people to buy things they don't really want or need. When I go to a store to buy something, if I find it's sold out, I'm pretty annoyed and don't feel like buying anything else.