There is no author or legislator of the moral law. It is simply valid in itself in the nature or essence of things. We become autonomous only when we obey it, because then our will aligns itself with the objectively valid law, and our choice follows the same law as that we give ourselves. We can think of rational faculty (or the idea - the pure rational concept, not exhibitable in experience) as the legislator or author of the law because reason recognizes an objective standard, and to that extent is already aligned with objective moral truth.

Descartes recommended that we distrust the senses and rely on the ... use of our intellect.

We usually can't know how, and we probably should not even ask, how our lives contribute to a better world.

Kant does represents a distinctively modern view of the human condition in contrast to that of ancient high culture, found in ancient Greek ethics and also in ancient Chinese ethics.

We are generally forced to choose one way or the other of distancing ourselves from Kant. I suppose I tend to choose the irreligious way. But I regret that Kant's path has not been followed.

Kant does not think there is anything wrong with being beneficent from sympathy. He thinks we have a duty to cultivate sympathetic feelings by participating in the situations of others and acquiring an understanding of them. He thinks we also have a duty to make ourselves into the kind of person for whom the recognition that something is our duty would be a sufficient incentive to do it (if no other incentives were available to us). That's what he means by "the duty to act from the motive of duty".

I think Fichte did take it further than Kant by arguing that we can regard the moral law as objectively valid only by seeing it as addressed to us by another being, even though Fichte thought God could not literally be a person who could address us.