You might come out of this film with a better understanding of the events that led to the 2008 financial crisis -- or you might not. More likely, I think, you'll sort-of understand it while you're watching, but be none the wiser when it's all over.
The question of what happened is explained, but not the one of how it was allowed to happen.
But I think the problem with this as a movie is that it tries to dramatise the events, using versions of some of the real people involved as characters; but it doesn't go far enough in that. We don't see anything of their lives outside of their financial dealings, so it fails to humanise them sufficiently. As characters, I ended up just finding them tiresome.
To really help us to understand the whole thing, it would need to be a documentary, and that would have been harder to sell. So by not quite being enough of one thing or the other, it fails at both.