This sounds like the broken window fallacy. You could use the same logic to suggest that Meta dump piles of cash on the sidewalk in front of their office - it’d circulate but it wouldn’t help them.
If the same $20bn was spent on fixing a bridge, people would spend those wages to boost economic activity AND have a fixed bridge that will improve output even more. Horizon Worlds isn't a productive use of capital in that regard.
It'd be one thing if they open-sourced their VR tech, some of that could lead to productive tech down the line, but as a private company, they're not obliged to do any of that.