There’s very little that’s easy and accessible about Dante’s style. By "formal," we mean that Dante adheres to a very rigid literary form. In this case, epic conventions include tons of invocations to the muses, epithets, apostrophes, epic similes, divine creatures, and a character list longer than the Encyclopedia Britannica.
The "elevated" part indicates that the text is difficult. Sentences tend to be extremely long and chock full of prepositional phases. This type of language tends to describe some larger-than-life topic – say, man’s eternal damnation – and to address it in a very serious, occasionally stuffy way.