Is religion man-made?

Based on the above diagram: Yes. All of them are by definition, "man-made".
Prophets are human.

Certain aspects of some religions may qualify as being inspired by spiritual experiences.

In history I believe that there have been times where a prophet has been tasked to create a religion to the best of their ability in order to teach and help other people and to fulfill certain purposes.

By my reasoning, the likelihood of even such an organization turning out to be flawless (or the people who labor within it) is very, very low.

However, also by my reasoning, the likelihood of some (or many) of the services, parables, stories, councils, doctrines, ordinances that are administered in such an organization to be more successful than the absence of all religion in encouraging people to have spiritual experiences of their own is high.

Those who have had no spiritual experiences consider them to be of no worth.
Those who have had spiritual experiences consider them to be of utmost worth.

Unfortunately, there is also a large 3rd group of people who have not had spiritual experiences, whose belief system is 100% based on confused traditions, pseudo-spiritual "warm fuzzy kitten" feelings, and repeated confirmation bias.

I am concerned that this large group of people often are the "poster child", and thus further persuade those who consider spiritual experiences to be of no worth in their position.