Since around 1975-80, when software makers stop'd giving you the source-code with the license to use it, and just gave you the compiled unchangeable product?

Not is it just acceptable, it's your obligation to tell peoples what the downside (or upside) of closed down software is. Is a closed source webserver a good idea? probably not. Is THE closed source Photo-editing program a good idea? Probably yes....if you really need it.