I don't think anyone is arguing that programming languages need to _keep adding_ features. I don't even think anyone is arguing that Go isn't successful already

I don't think anyone is arguing that programming languages need to _keep adding_ features. I don't even think anyone is arguing that Go isn't successful already. The argument is that the programming language should have the good features. Maybe that's an unwise stance, but it doesn't seem to be the one you're arguing against.