What Pope said, is that it is a dangerous notion to seek a personal relationship with Christ outside the Church. In other words, as Christians our relationship with Christ, puts us into a relationship with the entire Body of Christ.
St. Paul talked about this in detail in Ephesians 3, being saved by grace through faith, we become part of the Body and are In Christ.
In Corinthians he uses stronger language, saying the eye cannot say to the foot I don't need you. (1 Corinthians 12:21)
The Evangelical notion of being a Christian reduces it to me, Jesus, and my Bible and while we can not judge the ultimate salvation of any man, this notion is heresy. Certainly a personal relationship with Christ is necessary but, by definition, a relationship with Christ is a relationship with His Body, the Church.
Jesus taught us to pray, Our Father . . . not My Father, so look at the first word. Our — that is a personal plural possessive Pronoun. By saying My Father, you are using only a personal and possessive pronoun but by virtue of being Our Father it implies a relationship with the rest of the Christians on the Earth.
So that is what the Pope meant in context. No one on his own can take the Bible and discern doctrine, claiming to be lead by the Holy Spirit alone. On the contrary, this leads to massive confusion and about 40,000 different denominations at last count. All of them claim to be Bible-believing . . . the Bible being their only authority but they can't agree on much.
Jesus established a Church. He gave that Church teaching authority, by which we know what books belong in the Bible to begin with and through the Church, Christ gave us the sacraments which are His Divine Works, where He is present and we encounter Him in a True and Objective way.
Now, I have a lot respect for our Evangelical brothers and perhaps as Catholics we ought to stress a personal relationship differently. We tend to use sacramental language, which sadly a lot of Catholics don't even understand.
I'm not saying, nor was the Pope saying that these folks are damned but this notion leads to all kinds of heresy . . . all kinds of divisions . . . and worst of all, it keeps people from being part of the One Church Christ established.
Even using the Bible alone, the Bible teaches being part of a Christian Community. The author of Hebrews tells us to not neglect the assembly of the saints (believers). (Hebrews 10:23-25) Meaning Christianity is not a me-and-Jesus-alone religion or faith. It is a family faith — the family being the Body of Christ.
Hope this helps,