If you were telling someone to try on the shoes, could it make sense to tell them this without "신발"?
I believe that you could if the shoes were already part of the conversation, but to ask someone to try on something (on the feet) you might have to specify i.e. socks, shoes, dress shoes, etc.
More precisely, without 신발을
What's the difference between 신발 and 구두?
신발 has wide meaning, same with shoes, but 구두 only directs shoes which are worn with suit