I don't think there was any compromise at all. Ridley Scott and Callie Khouri rightly served the story first and foremost, not the external politics or causes.

Looking at this logically, Callie Khouri had three choices: 1) They escape to Mexico. 2) They get caught by police and punished (perhaps not as severely as expected, due to various mitigating circumstances, but they still wind up in prison). 3) The ending we got.

Ending 1 would have felt as though it belonged in a different film. The whole tone of this feels as though it is building to a Butch/Cassidy type scenario. Ending 2 would have been realistic, but dramatically inert. Ending 3 on the other hand gives the story real emotional heft and tragic dramatic weight. I don't think we'd still be discussing the film (and it's themes) today if it had a different ending. Ultimately, I like the ending because it feels right for this story, not because it is self-consciously attempting to spearhead a cause.

Obviously, how one reacts to the ending depends on personality, temperament, upbringing, and so on, but I certainly don't think young girls would automatically slide into apathy over feminist issues just because they see a (satisfyingly) tragic end of this kind. Ultimately stories need the right ending rather than the right-on ending, and I think in this case that was judged perfectly. :)