At least for me, the idea that a game might someday be unplayable for me doesn't stop me from wanting to enjoy it. I like multiplayer games, and I have neither the means nor interest to host my own servers for them. I've gotten far more than $40 worth of entertainment from Helldivers 2. I think games should stay accessible and not be killed when servers stop hosting, and be available to play offline. However, the lack of those things won't stop me from enjoying something now. I don't consider that money lost, it's spent, as long as I got an equivalent value of entertainment. I didn't set my money on fire, I've gotten hundreds of hours of fun, far more than $40 could buy me elsewhere. I expect to continue enjoying helldivers for years.

You're absolutely right, that games shouldn't be killed when they're no longer supported, and that they should be playable offline and LAN. As things stand though, it's the same as spending money on an amusement park, or movie, or any other form of entertainment. If you're not going to be able to enjoy it without those things, that's your prerogative, but I think you could easily get your money's worth, especially compared to overpriced AAA competitors.