Go appears to be made with radical focus on a niche that isn't particularly well specified outside the heads of its benevolent directorate for life. Opinionated to the point of "if you use Go outside that unnamed niche you got no-one to blame but yourself". Could almost be called a solution looking for a problem. But it also appears to be quite successful at finding problem-fit, no doubt helped by the clarity of that focus. They've been very open about what they consider Go no to be or ever become. Unlike practically every other language, they all seem to eventually fall into the trap of advertising themselves with what boils down to "in a pinch you could also use it for everything else".

It's quite plausible that before Go, its creators would have chosen C++ for problems they consider in "The Go Niche". That would be perfectly sufficient to declare it a C++ replacement in that niche. Just not a universal C++ replacement.