Well, I don’t think the Holy Spirit is the author of confusion, so at one level, I would say it is not the will of God to move people away from the fullness of the Catholic faith. In other words, those who are in Full communion with the Catholic Church. Now, if someone had already fallen away into atheism or agnosticism, and by the prompting of the Holy Spirit, a person finds himself in a Protestant confession, that is a different matter.
So again, if the question is it better for someone to leave the Catholic Church, the answer is no. The best thing for them is to embrace Catholic orthodoxy. If someone has fallen away completely, then yes, it is better for them to be practing the Christian faith in a Protestant Church, and I would add, one that holds to historic Creeds (e.g. Traditional Anglicans, Lutheran or Reformed), would be the best ones, IMO.
So, there is only One Church, as Christ has only One Body and One Bride. So, all that who are Baptized, whehter they no it or not, are in some way related, to the “One Holy, Catholic and Apostolic Church”.
It is Catholic ecclessiology that Christ’s grace if most fully present in the Catholic Church by virture of Apostolic Succession. For as St. Paul stated, the Church and the Apostles and their co-workers were the “stewardships of God’s grace” (c.f. Eph 3:2) and “stewards of the mysteries of God” (c.f. 1 Cor 4:1). The Greek word mysterion (mystery) was translated into Sacrament by St. Jerome, and is thus the normative means through which God’s gives us Grace.
Thus, the Catholic Church (and Eastern Orthdox, for that matter), by virture of Apostolic Succession and valid priesthood, has valid 7 sacraments, so that Christ, through his body, the Church and the sacraments, sanctifies humanity. Accordingly, the fullness of Grace is present in the Catholic Church.
Does that at least get at what you are asking.
Yes. We must agreeably disagree.