Are you [or this declaration] saying then that a person could be a baptized, confirmed, sacrament-receiving member of the laity, but if he [she] does not accept all of the Church’s official teachings, then that person is actually a non-Catholic in the eyes of RCC???
Yes, well-informed rejection of any dogma of the faith excommunicates. He may have an excuse if he is not well informed of the doctrine, or struggles to accept it, or if it is a lapse into sin and he confesses it, but not if the doctrine says one thing and he does another.
Classic examples are politicians promoting abortion “rights” or couples cohabitating or contracepting.