Which subsector of charitable nonprofits is the least professionalized?

Religious Organizations.

Explanation:

A religious reason for existing is one of the seven absolved purposes determined in Sections of the Internal Revenue Code. Be that as it may, not at all like with the expressions "magnanimous," "instructive," and "logical," the expression "religious" isn't characterized in the Treasury Regulations, in expansive part because of established issues. IRS direction clarifies under the First Amendment, the Service can't consider the substance or wellsprings of a teaching asserted to comprise a specific religion, and can't assess the substance of a tenet an association claims is religious. This does not make a difference to rituals or practices that abuse government, state or nearby law.