If you mean his articulation of "Anonymous Christianity," Archbishop Lefebvre was certainly mistaken. He reformulated by dogma no salvation outside the Church as no salvation except by means of the Church (or though the Church). Archbishop Lefebvre was not a trained theologian by any stretch, and he probably was led astray by a professor of his that he considered otherwise orthodox and Traditional.
Right. The modern notion of EENS is very ambiguous and subjective. Contrast that to St Augustine, St Thomas, the Church Fathers and even many theologians of the 1800/1900s. The great archbishop George Hay (d 1811) is staunchly pro-EENS in the orthodox and strict sense. In his book "The Sincere Christian" he discusses this dogma as it is found in Scripture.
Father Feeney rightly identified EENS-denial as THE core problem with the Church already in the late 1940s.
Right, and Fr Feeney was living in America. The corruption and liberalism in Europe and France (where +ABL grew up) was far worse than America in those days. The most liberal clerics at V2 were from France and Germany.
Let's not pretend that +ABL was somehow immune from liberalism; he was only human. And let's not pretend that the sspx, even in the early days of the 1970s, didn't take heat for their watered-down beliefs concerning EENS. They took a lot of heat.
Take all the 'hot button' issues of Traditionalism today (EENS/BOD, Sedevacantism, R&R, Jurisdiction, etc) and now imagine 50 years ago, when Traditionalism was just starting in the 70s. In those days, the 'hot button' issues were the new mass, V2, and EENS/BOD.
The controversy/debate over EENS/BOD has never gone away; it's been around LONG before V2 and now, afterwards. The reason is because EENS is so important to the Faith and this doctrine has been violently attacked by satan ever since God allowed the Church to enter the 5th age, with the dawn of Protestantism in 1517. The Council of Trent did a great job defending this doctrine in the late 1500s, but since then, it's been all downhill...
But the doctrine, since it's Divine Truth, won't go away. Just as many disciples walked away from Christ's doctrine of the Eucharist in John 6 (calling it "difficult"), so many catholics try to widen the "narrow road" to heaven, calling it "too harsh".