I think some of it is the audience's fault. I have heard many friends complaining about multiplayer games being "dead" or "abandoned" because there's no new content and I'm like "I'm pretty satisfied, it doesn't need anything else". If there's enough people playing for matchmaking, I'm good.

Let's change that expectation. Baldur's Gate 3 won best multiplayer at the Game Awards, and it's not a live service. In a talk with some friends, I realized how antagonistic the relationship between players and developers always ended up as well when the developers make more money with more "engagement". Diablo IV will get fun builds nerfed into the ground; Baldur's Gate 3 will let them rock, but only in the pre-existing difficulty levels before they add in extra challenge modes for fun. That's the difference.

Meanwhile, Agent Under Fire multiplayer for the Gamecube is more fun than any live service FPS I've ever played. It certainly didn't require years of support to be that fun, and you only need one other person to play it with, but preferably 3. Very easily doable regardless of how many people are in matchmaking.