I don't think the movie even necessarily takes a hard position on a lot of its moral dilemmas. After all, it ultimately portrayed basically all the Wakandan cast as sympathetic, and they advocated positions all over the spectrum. Stepping out into the light and helping the world is certainly T'Challa's position, and portrayed as probably the best decision, but that's not the same as saying all other choices are wrong and evil, and always were even into the past.
Note that the one choice the movie went out of its way to declare as wrong was T'Chaka leaving Erik an orphan out in the world. *That* got condemned, pretty explicitly, and even T'Chaka pretty much accepted "Yeah, I screwed that up". The framing really read to me, though, that T'Challa's changing course from past policy wasn't him morally rejecting the choices of his predecessors. It was that, on realizing his father was not perfect, he felt the confidence to step out from the shadow, and make his own decisions firmly as king.
( Which will probably mean, thematically, that future movies will have him making his own, new and innovative mistakes. *eg* )