Live service makes sense when done right. Fortnite shows a good idea of it working. Heck GTA Online shows good ideas.

I would love a game where if you bought a different game, you could play that character or that mode. So you have Mario Kart World, you bought the new Donkey Kong game, so you can now play Donkey Kong with enemies in Mario Kart World. People could be racing and you're battling various animals. Then someone skateboards by while Sonic the Hedgehog runs for some rings. I would love to create a character and give him the powers of the various games bought. Then team up or go against various people who bought other games.

I would love that, but I doubt anyone would make it.