It's not about the lyrics being deep almost no lyrics in any popular music are deep except in a im14andthisisdeep sense. It's usually about not understanding regional slang or inside jokes.
For example I really like grime but I haven't lived in England for over a decade so I have no clue what a lot of their references mean when I first hear them because I never hear them in my day to day. Genius helps with that and a lot of other cases.
I never found most hip-hop lyrics being so deep that hey need some annotations for explanation.
Then it felt like very far fetched to me that people who considered annotating hip-hop lyrics now want to "annotate the world".
And now they can't live up to their promises, which perfectly fits in my, probably wrong, model of hip-hop culture in general.