
Thinking back to a post I saw the other day where the original poster was asking why Wakanda didn't do anything to stop the slave trade or the colonizing, given their technological superiority. My answer at the time was that such a tiny nation shouldn't be expected to police the whole world. But a much better answer I thought of just now: There isn't any evidence to suggest Wakanda had technological superiority, at least until recently.
Before you respond, hear me out: the vibranium wasn't some crashed spaceship, or sentient metal that could imbue secret technology knowledge. It was just a metal that was in a meteorite that hit Africa at some point in the past, that humans later found. I know I'm not a big comics nerd, but going by the movies, we don't really know a lot about vibranium. For all we know, it could be as easy to get out of the ground as copper. And the museum scene featured vibranium spears that looked a lot like other weapons from the area and era, just with a different metal than other cultures were using. So it shows there was a progression of technology.
My theory is this: Wakanda was naturally isolated at first. We know there are mountains in the area, I'm thinking maybe a valley surrounded by impassible mountains. Maybe long ago, one or two tribes of people stumbled onto the only entrance to the area and later brought others into the area because hey, free land nobody else is using. Then they just would've had to guard the only entrance to the valley, pretty easy to do. May even be the reason for the difference in culture between the mountain Wakandans and those who weren't in the mountains, IE the mountain Wakandans being in the mountains to guard the entrance/exit.
That alone would be enough to explain a lot of Wakanda's history of isolation. But I'm also thinking an isolated group like that doesn't have a lot of reason to advance technologically, at least not until reports start coming in from the rest of the continent (maybe there's a tradition of a small group of people exploring outside of the valley to get a feel for any changes in the surround area) of dangerous pale people with guns and cannons going about stealing land and people. Even more reason to be isolationist, especially if they're still using spears and shields. Sure, it's vibranium, but how much does that help against guns and cannons? These are still just normal people, apart from the Black Panther.
So, over time they realize the white plague of colonizers is spreading. These foreigners are doing all kinds of crazy things like climbing tall mountains just because they're there. There may even be rumors among the locals of a hidden tribe of people up in the mountains of Wakanda. Reports come in of great armies of warriors mowed down by metal exploding tubes shooting metal balls at high speeds; peoples who were once considered top dog of the area turn into kicked puppies.
Point is, they realize they're not safe anymore. Maybe they send one of the earlier Black Panthers out to steal some guns and cannons, or just books about these things and other tech of the colonizers so they can make their own, increase their odds. Then they get reports of groups using stolen guns and cannons against the invaders and still getting their asses kicked. So they start trying to find other ways, better ways, just in case. Until then, the Black Panther and the mountain guards keep a close eye on the mountains and the area around them, killing anyone who approaches too closely, like the people of North Sentinel Island still do to this day.
Now the real kicker to my theory is that we don't have a timeline for any of this technology, not as far as I'm aware. For all we know, they didn't have the cloaking shields and laser cannons and whatnot until the last 30 to 100 years. My thought is that the news of the invention of hot air balloons stirred them into finding better ways of hiding. Then airplanes came along and made this even more important. Not sure what they would have done for most of those decades, but at some point they were motivated enough to invent cloaking shields, maybe just in time to hide them from cameras in space or on spy jets. Nothing to see here, folks, just a bunch of mountains nobody can summit without dying.
And that's basically my theory. TL;DR, Wakanda only recently came into their advanced technology because vibranium does not inherently confer any technological advantages. They didn't do anything about slavery or colonizing because they were at a technological disadvantage, and just trying to survive. And it took the events of the Black Panther movie for them to finally realize they didn't have any reason to be scared anymore; they had finally surpassed the tech of their enemies.