Starbound. Waited years while it was in development, and my buddies and I just let the hype build and build. When it finally came out, it wasn’t even close to worth it. At the time, it still seemed like something that would eventually get to where we hoped (or at least for the most part), but picking it up every few months/years showed us the dev team’s ideas were great on paper, but they just weren’t capable of implementing any of it well.
More recently, I’ve seen YouTube docs that have gone into the awful development and bad treatment of young developers who weren’t paid, and fired after they caught on that they never would be.
On the bright side, it gave my friends and I a new appreciation for how great Terraria is, and why it’s similar features work so well when Starbound’s didn’t