VRChat is also consistently active with people making new worlds/maps, avatars, etc. There also used to be a client modding scene with e.g. melonloader but that got cracked down on around 2022. The "metaverse" however, does it even exist? Is there a vrchat-like, meta-built social vr environment available on quest hardware?

No idea, which is notable because I boot into my Meta Quest 3 most nights for sim racing. You'd think I'd have seen it if they were pushing it.

I am glad they don't, the headset should be a general computing device first and foremost, launching apps you choose to participate in.