It's indeed a pity they ditched triples and rotations. I don't think it's about players only caring about singles though. It's just the developers not investing enough into actually getting players to interact with the format. It's similar to what happened with Battle Royals in gen 7. They never introduced any Battle Royal in any kind of ranked format. No online competitions, no friendly competitions, no simple rated battles, and no PGL support. They're just an option on the free battle spot. And in the story they're introduced fairly early on, you get one introduction battle, and if you then like it and want to try more, well, the opponents are all level 50 and they're legendaries and mega evolutions and so on, while at that point in the story your team basically is a level 22 Brionne, level 21 Trumbeak, level 20 Gumshoes, and so on. So as a player you stand no chance and you just get destroyed. Battle Royals are never mentioned again after that. And it's a darn shame, because the format itself is super interesting and lends itself to quite a couple of pokémon that don't see too much action in the other formats (for instance Starmie, Scizor, and Manectric are amazing in Royals). It's not like the format itself is broken or anything, the mechanics are fairly well balanced as long as you keep Magearna and some overpowered legendaries like Kyogre banned. Had they adjusted the level requirements better to what teams players would have had during the story (like what they did with the introductory battle facilities in Emerald before the Frontier), had some repeated occurences in the story, a proper rated format for it including PGL support, and an online competition or two for it, it could have been so much more popular and actually taken off. But when the initial trigger is missing, there are initially already fewer people playing the format on the free battle spot, and as it already takes four people to even initiate a battle, the game will usually just fail to find sufficient other people to start a royal, which isn't exactly encouraging to keep on trying either. Had it been easier to find battles I would have also tried way more to do Battle Royals on the battle spot.