I think it was both the horrible technical implementation and the full and total control they demanded over it. It's like what I would imagine the Oasis to look like ten years after the bad guys won in Ready Player One.

The internet only succeeded because it was so free and open at the beginning, decentralized, open protocols, everything free, no borders, no censorship, no surveillance just hackers that layed the foundation with no restrictions placed upon them (except the severe technical limitations of the time for them to overcome). Of course that's almost all gone now with capitalism taking over turning everything to shit, but that came only after it already was successful.

Meta's vision and implementation of the metaverse was exactly the opposite end of the spectrum in every way from the start: centralized, commercial, proprietary, censored, surveilled, restricted, closed, walls everywhere, safe, advertiser friendly, it was uncool, not fun and no style. Like they paid people to create shitty "worlds" and force their employees to use it, otherwise nobody touched that shitshow willingly, except (concerningly) for some random toddlers for some reason.