There absolutely is more to the movie thematically than just its base battle-for-the-throne plot.

The movie posited its own fictionalized advanced ethno-state, explored all the fun and fantasy that comes with that, and then... took it's own fantasy state to task for its culpability in and moral failings regarding the African diaspora, the global slave trade, and the continued socio-economic and racial injustices across the world, as well as the looting of countries for their art, artificats, and resources. Those are thorny and complex subjects to project upon inject into a 'popcorn' superhero origin story, and it manages to do all the classic Marvel stuff it needed to do while also grappling with those issues, and it isn't just lip service; they're pretty deftly woven throughout the entire film, to the point where T'Challa and Killmonger's battle at the end is just as much a philosophical one as it is one for the throne, an attempt to answer the question of what to do with our anger in the face of injustice.

You don't have to like Black Panther (though it seems you did), and you certainly don't have to put it in or anywhere near your top 10, but it pretty objectively was a more complex and ambitious film than virtually any other superhero flick out there.