An "alternative" doesn't mean "has to be as good or better at everything that C++ does".

Most programs don't have garbage collection latency issues. Look at Android or Windows Phone - all the user-level apps are written in garbage-collected language and they work just fine.

Look at web - all the interaction is written in JavaScript and Gmail works just fine.

At this point in the discussion people usually bring "real time" applications. Approximately no-one writes those applications.

Go is an alternative to C++ in the sense that many (but not all) programs that you had to write in C++ you can now write in Go.