I was directly answering the GP poster's posed question. Let me rearrange that question for readability:
> Why do people "worry" about Zig potentially never becoming mainstream?
There are people who want to learn Zig because they're excited to gradually transition their way away from some other ecosystem, and into the Zig ecosystem, as the Zig ecosystem takes root and develops.
But they don't want to regret that decision. They don't want to end up in a place where they're writing blog posts about how much they love Zig, and are the maintainer of five popular Zig libraries, and yet still feel forced to use C++ for their next actual app project (where they're then mostly unable to make use of those Zig libraries!) just because Zig, not being sufficiently "mainstream", can't attract/force the corporate owners of big fat libraries (Vulkan, CUDA, LLVM, etc) to invest effort into integrating with it, and continuously maintaining those integrations for it (i.e. including a Zig build in their CI matrix, so that their upstream changes can't silently break that integration.)
> Why do people "worry" about Zig potentially never becoming mainstream?
There are people who want to learn Zig because they're excited to gradually transition their way away from some other ecosystem, and into the Zig ecosystem, as the Zig ecosystem takes root and develops.
But they don't want to regret that decision. They don't want to end up in a place where they're writing blog posts about how much they love Zig, and are the maintainer of five popular Zig libraries, and yet still feel forced to use C++ for their next actual app project (where they're then mostly unable to make use of those Zig libraries!) just because Zig, not being sufficiently "mainstream", can't attract/force the corporate owners of big fat libraries (Vulkan, CUDA, LLVM, etc) to invest effort into integrating with it, and continuously maintaining those integrations for it (i.e. including a Zig build in their CI matrix, so that their upstream changes can't silently break that integration.)