This was at a time when there was still some doubt about what was happening and what it meant. Rome was till substantially Catholic.
That time has long since departed as that is no longer the case.
The Lefevbre brand does not have the magic that it once had because its arguments have been long overtaken, in the practical sense, by the collapse of the Church.
Agreed. Lefevbre's caution was fitting the situation he lived in, and yet he clearly did not recognise the full authority of Pope John Paul II as he ignored his orders under the pain of excommunication, and he never recognised his excommunicated status.
The R&R crowd have to believe that the founder of their own movement was excommunicated and damned to Hell by accepting the Conciliar Popes as valid Popes, and yet they still continue despite that. Either these Popes are valid and the founder of the SSPX died an excommunicated man, in which case they should all leave the society and stop honouring him as they do, or the Popes are not valid(in which case they're sedevacantists and not R&R at all).