As long as there is a singleton that does everything that we (humanity) want, as long as we are inferior to it, all possible problems are artificially created problems that we have chosen to solve the slow way.

I am basically alright with that, considering that "artificial problems" would still include social challenge. Much of art and sport and games and competition and the other enjoyable aspects of multi-ape-systems would probably still go on in some form; certainly as I understand the choices available to me I would definitely prefer that they do.

Could you imagine reading science fiction in a world where a process like CEV makes sure that the whole universe suits the needs of humanity?

Yes, absolutely I can.

Right now, we write and read lots and lots of fiction about times from the past that we would not like to live in. Or, about variations on those periods with some extra fun stuff (i.e. magic spells, fire-breathing dragons, benevolent non-figurehead monarchies) that are nonetheless not safe or comfortable places to live. It can be very entertaining and engaging to read about worlds that we ourselves would not want to be stuck in, such as a historical-fantasy novel about the year 2000 when people could still die of natural causes, despite having flying broomsticks.