Traditionalists need to identify the cause of the old ecclesiology.Ecclesiology should not be identified with the Mass. It is independent of the Mass.
There can be the old ecclesiology based on the strict interpretation of the dogma extra ecclesiam nulla salus.So with this old ecclesiology a Catholic can attend Mass knowing that the Church teaches that Jews and other non Catholics need to convert for salvation.
While there can be Catholics who attend the Traditional Latin Mass who affirm the new ecclesiology, the new theology, which comes from the objective mistake made in the Letter of the Holy Office 1949 which was not known even to Archbishop Lefebvre.
When the Jewish Left are aware of this they would probably consider Vatican Council II Anti-Semitic.
The Letter made a mistake. Archbishop Lefebvre did not notice it.
False reasoning from the Letter is all over Vatican Council II: Abp Lefebvre did not notice it -1
False reasoning from the Letter is all over Vatican Council II:Abp Lefebvre did not notice it -2