They are close to the Pythagorean sounds. But, only the octaves are pure. All of the other intervals are impure. No key sounds bad. No key sounds pure.
All keys are somewhat interesting.
But, they are all the same. Most music, from the middle of the 19th Century until now, has been written for equal tempering. England stayed with well tempering, long after the rest of Europe had switched to equal tempering. We now live in a world where Bach will probably be played on a well tempered instrument. Medieval music may be performed using a Pythagorean scale.