I use to be the director of marketing for a company in the gaming industry. Without giving too much away, my department had the task of finding out who currently owned a bunch of 8-16 bit retro games and negotiate licensing deals. I expected the project to take some time and prioritized the list of games I would go after and gave it to one of my team members who had a ton of historical knowledge about the industry. Not much progress was made so I decided to spend a bit of time on it myself. The whole thing devolved into a time sink of detective work to find out who currently owned what game, and at the conclusion of that everything turned into phone tag hell. Some people I spoke too simply did not know for sure if their company was legally able to licence a game. Some of these people had not really been approached with anyone trying to make a deal like this before and wanted too much money, I guess because there was no historical precedence for what a "good deal" was. And to my surprise, many people were not even interested in making a deal on some unproductive IP/game despite it being a way for them to make money without lifting a finger. The only companies who you can make a deal with quickly are the larger ones that never had any of their IPs change hands and know exactly what they are doing by milking these old games, like Sega and Capcom. I could not go after them for this specific project due to political reasons.
The prioritized list I made got shorter and shorter until I canceled the whole project. Even if only time was wasted on it, it was one of the few projects I took on that ended in complete failure. It actually makes me feel a bit better to see that this Nintendo plug and play has only first party games, or games that were made by companies that still exist today. I'd bet you any amount of money whoever at Nintendo was tasked to make this machine happen ran into the same nightmare I did, then stripped the project down to just Nintendo games and a handful of other games from companies who have just always been around since the 80s/90s.