I arrived really late to this conversation, but Wakanda at least as it is portrayed on the film is not only a head scratcher but a by the numbers impossibility.
To put it short Wakanda at best would be like Cuba since culturally and intellectually speaking are tied to their neighbours but are isolated. They have the best Egypt, Aksum and Mali have to offer but worth nothing if they cannot keep Islam and Christianity outside, difficult since these religions have strong ties to these regions.
Their weapons and army doesn't mean anything if they cant put it on the market legally, and we can assume they are "allies" to major powers since they are present in several meetings, yet is expected they are in permanent state of scrutiny. If we have a Mansa Musa case it doesnt change since we are supposed to believe Wakanda is a free monarchy.
According to all data on their in real life location they have a vast territory populated by several ethnic groups, including all the variations of bantu, cushitic and mali people available. These groups don't tend to get along. Is even believed if Africa was never colonized nations as big as Congo would never been formed, at best you get bloody empires and Wakanda would have competence on each corner if it is that big.
Science, math and literature were for the most part an import from muslim empires. Wakanda will be trapped with outdated principles.
The best factor on why Wakanda could become a power is the same to Europe and Asia, but the Sahara acts as a natural buffer.