The game almost definitely has an EULA that covers this exact situation.

Class action lawsuits only work if a law has been broken.

I guess you could say that the consumers chose to buy the game, knowing that it had a dependency on an online service that they weren’t being charged an ongoing cost for. Obviously that’s a bit of a cop-out answer, but I I agree with you that if game companies shut down their servers, they should release the server code. Or at very least the API of the server so that it can be reverse engineered more easily.

I think it’s more just that the server running cost is an ongoing cost, while each purchase of the game is a one-time cost. So even though the server cost is likely very low (all it does is host level designs and some metadata around them), eventually sales for the game were bound to drop to the point that they would be losing money on the servers. Honestly, given how poorly the WiiU sold and how long ago it came out, I’m surprised they kept it going this long, but I supposed that just speaks to the cheapness of the server running cost.

Because not enough people are buying it to justify the server running costs?

Combining things that haven’t been combined before is the quintessential creative act. Because as you said, there is nothing new under the sun. But there are new ways of combining those things.