Does Magnus Carlsen still have what it takes?

How should we know?
He played classical twice this year with good results but lost against Pragg and Fedoseev.
At what point would you stop saying, "Carlsen could easily be World Champion if he just cared enough"?

If someone like Caruana wins the WC against Gukesh, would he be considered the true World Champion while Carlson is still Number One on the Elo list?

If we only define The Best in terms of Elo and if Carlsen just sits on his classical Elo from now on like Anand, how are we going to know if he still has what it takes?

How can you be considered the best player in the world when you do not compete regularly and shy away from competition?