I dont agree. I see what you're saying. Elton John and Billy Joel can't make hits anymore. But I don't think it's their ability. It's their style and sound. The moment has passed and the market has already moved past them. That's what impressive about Kanye. He keeps reinventing his own sound and constantly leaves behind the stuff that made him popular in the past.
I can say that about Nas too. That's why when you say he can't flow and rap like he used to. That makes no sense. That well has dried up and rapping like he used to means outdating himself. I think Nas has always ridden the edge and he sounds pretty energetic here. Same with the sound that Kanye is serving. It's on the edge of the market's taste so some people might not get it yet. It's a bit too new and the crowd isn't used to it.
A lot of the old heads keep serving the old shyt and it's dated and predictable. I enjoy this album more than LIG because it's fresh.
As I said in my first reply, I wouldn't say that about Nas. But it's abundantly clear in Hip-Hop. Snoop Dogg, Kurupt, Styles P, Talib Kweli... Actually a really good example is ROYCE.
Your brain has to be sharp, and active, to create a good flow. As you grow older, you become complacent with your craft, your brain begins to focus on other things in life, for some alot of drugs will fukk your flow up. These same things can also fukk up your ability to write good lyrics, just like it can affect a guitarists ability to think of cutting edge riffs, and be able to play them too.
It's directly relatable to sports, as your metabolism begins to fade from old age, your creativity in making plays fades, even your mind's ability to read plays fade.
This applies to all things in life really, because it's just what happens in life when you get old. Yes people like Nas and Kanye have managed to stay relevant and pivot after their 40s, but that's extremely rare. Just like there's those odd gems in sports that are very dedicated, or are smart enough to use the tools they have left and their experience to approach the game differently in order to be successful.