I like Kendrick, but the example track you give is exemplary of my first comment: it is not pushing any boundaries musically. It is literally a jazz piece, used as backing for a very lyrical rap. A jazz piece even, that already solidified in the jazz era of the early 20th century. Musically Kendricks track pushes no boundaries and is an easily recognized style that exists for almost a century.
Of course Kendricks work is pushing boundaries. He has an excellent produced voice, the rap a timbre and meter that is fresh. These are musical components of his words, but mere details in all the music in this track. However, the words in his rap are not details.
Personally I have never been into words in music. I barely could hear them growing up listening to metal, and still only register a phrase or two in music today. If you see music and lyrics as different things, I see how you would give rap a bad rap, musically speaking.
There's countless examples of rappers incorporating, collaborating with and evolving every genre. One of my favs: https://www.youtube.com/watch?v=_ZTYgq4EoRo