The Catholic church disagrees with yout premise. They do not take the position that “homosexuality” is only a behavior. It’s just that the Catholic church condems all sexual behavior outside of marriage, and marriage is only the marriage of one man and one woman. EVERYONE outside of marriage is to remain chaste, if they are a faithful Catholic.
\You are mixing up 2 distinct issues. One, does the RCC believe that homosexuality is a sin. If not they should agree to gay marriage. Two, chastity is not possible for homosexuals. It is a contradiction in terms. So long as the RCC tries to normalize homosexuality and make it chaste they will continue ordaining gay priests and will skirt dangerously close to making sin a sacrament.