No, it isn’t ‘strictly’ Catholic viewpoint. (sigh). It is truth, and remains truth whether it is ‘called’ Catholic or not. It was true before Catholicism was brought to earthly birth through the resurrection of Christ (which is why those righteous who died before His sacrifice were saved, though the heavens did not open for them until Christ opened them with his resurrection). It remains true now, for those who are in ignorance of Christ yet still, mysteriously, through His Church, which is The Body of Christ, be saved through Him. (There is no other name by which we are saved).
The means through which God has chosen to save any of us is through His Son, and the means His Son gave for salvation is the Catholic Church, to whom He gave the message to “go forth and preach the good news, baptizing in the name of the Father, the Son, and the Holy Spirit”, the power to ‘bind and loose’, and the promise that “you are Peter, and upon this rock I will build my church, and the gates of hell shall not overcome it”.
Therefore our obligation to share the gospel, both through word and by example, is unceasing, in order to bring about to the world the desire for baptism, explicit or implicit, through the knowledge of Christ and His church. This is a reason why ecumenism in the sense that Catholics use it is so important. Unity to the one true faith is very important, otherwise we are back to the time of Paul when he exhorts the believers not to fragment themselves by saying that “I belong to Paul, I belong to Apollos” etc. but that all belong to God.
No wonder that so many nonChristians are confused today, when the thrust of the gospels has shifted from “let us tell you about Jesus Christ and His teachings” into “let ME tell you about Jesus Christ and what I THINK are his teachings.”
Not that I am saying that Protestants are ‘lesser’ or 'not as good" as Catholics. Not individually. Heck, many Protestants know more about their faith and act more Christ like than many Catholics. But. . .and it’s a big but. . .we aren’t talking about preaching the gospel of “Hank Hill the Baptist who is a better Christian than Carla Tortelli the Catholic”. What matters is that even the most Christ like Protestant lacks the fullness of truth in his/her denominational teachings.
If I’m teaching Math and I teach people addition, and subtraction, but totally leave out multiplication and division, they don’t get a complete enough picture to function. Sure, they ‘could’ figure out multiplication and/or division on their own. . .but they might not. The consequences for the lack of fullness of teaching can range from nominal to catastrophic.