I believe it depends on your field. In my branch of experimental physics (a long time ago), coming up with a viable problem was your advisor's job! To do a good experiment required collaboration, substantial grant funding, and (hotly competed for) accelerator time. Not a good idea to let a student sink or swim in that environment; the most likely result would have been to sink, which does no one any good.
But more generally, coming up with a good research problem in the sciences can be a sophisticated skill that develops over years of experience. I imagine some grad students might have a precocious talent for this, or they might just get lucky, but it's definitely not something that every beginning grad student has. (Again, at least in some fields.)
But more generally, coming up with a good research problem in the sciences can be a sophisticated skill that develops over years of experience. I imagine some grad students might have a precocious talent for this, or they might just get lucky, but it's definitely not something that every beginning grad student has. (Again, at least in some fields.)