The picture of Rosie the Riveter is often combined with the phrase "We can do it!". The phrase Ni povas fari ĝin! is a literal translation that is correct - but does it really capture the essence of this phrase? I don't think so, because the meaning is more like "We'll make it!". There is no literal it involved.
Could someone suggest a better translation?
As you say, "Ni povas fari ĝin" isn't wrong, but we can probably do better.
"Ni sukcesos!" is simple and to the point. "Ni venkos!" adds the aspect of overcoming an enemy without directly referring to them.
My proposal is "Ni kapablas!". I am no expert on the history but I suppose the goal of the phrase is to show that women are capable to do work or bring change.
