It's 'useless' trying to change her mind. = It's 'useless' to try to change her mind.
Drugs are 'useless' in treating the condition.
I made a 'useless' attempt at fixing the leak.
(..) Thank you. - Hi. - Hi. Can you get me an interview with Corleone? No. I'm a relative, but I can't do that. What else can I do for you? - Handsome, but useless. - Oh, yeah? - That's okay, I'll gamble. - Do you like to gamble? Let's go to Atlantic City. I'll show you how to gamble. Well... (..)1990 The Godfather Part III