I suspect just about all who claim to be Christians would agree with this. But it just moves the disagreement to one about which issues are essentials and which are non-essentials.
The subject here is whether being in the wrong church or denomination will exclude you from heaven.
Let's go back to the early Church. There were multitudes of competing groups then, just as now.
Question for you: Would being a member of a Gnostic sect or an Arian exclude you from heaven? How about a Manichaean?
All these groups claimed to have faith in God and Christ, no matter how much they disagreed on who They were.
Yet most Christians of today would consider them to have been severely misguided, with their heresy varying from mild to extreme.
Presumably you, like most, would exclude some of these groups from the name "Christian." So what is the objective measure you use to draw the line? You claim there is no line, but I suspect you have one, though you might draw it in a different place than the author of the article above.
The measure is Christ. What do they say about Him and what do they say He did about Sin? If they say He is not unique and not God can I say they are a Christian Denomination? No. If they say there is no such thing as Sin? Heaven's no.
Without those, they would be a Cult. But who would I be to say that none of the elect of God within them would not go to Heaven? Do I recommend them No. Do I say there will not be trouble, No. But who would I be to deny God?