If you actually listen to how Zuck defines the metaverse, it's not Horizons or even a VR headset. That's what pundits say, most of whom love pointing out big failures more than they like thinking deeply.
He sees the metaverse as the entire shared online space that evolves into a more multi-user collaborative model with more human-centric input/output devices than a computer and phone. It includes co-presence, mixed reality, social sites like Instagram and Facebook as well as online gaming, real-world augments, multiuser communities like Roblox, and "world apps" like VRChat or Horizons.
Access methods may be via a VR headset, or smart glasses, or just sensors that alert you to nearby augmented sites that you can then access on your phone - think Pokemon Go with gyms located at historical real-world sites.
That's what $50B has been spent on, and it's definitely a work in progress. But it sure doesn't seem dead based on the fact that more Quest headsets have been sold than this gen's Xboxes; Apple released Vision Pro; Rayban Smart Glasses are selling pretty well; new devices are planned from Google, Valve, and others; and remote work is an unkillable force.
The online and "real" worlds are only getting more connected, and it seems like a smart bet to try to drive what the next generation looks like. I wouldn't say the $50B was spent efficiently, but I understand that forging a new path means making lots of missteps. You still get somewhere new though, and if it's a worthwhile destination then many people will be following right behind you.