The essential problem with Plinio as I see it is that he wasn't very transparent with his organization. TFP wasn't a religious order, but it also demanded much more from its members than a lay organization ever would or had a right to. While he was alive, he was mostly well known for going after Communism, but he stopped short of VII. Going by Atila's account, he would have publicly endorsed the Murky Waters book had he lived to see its publication but as it stood, it was almost 30 years after SSPX had already been duking it out in the public square. Many people voiced concerns privately during and after the council, but almost no one had the courage to stand up to it. Plinio, Atila, and the TFP were no exception to that rule for the first 30 years but Abp. Lefebvre and the SSPX were.
That is not to say that newcomers aren't welcome but when TIA wants to suddenly build up Plinio as some great leader of traditionalism ahead of the Archbishop, that's when they have to learn their place.
Archbishop Lefebvre was tasked with having to navigate through the corrupted hierarchy of the Church, a path he had to chart without much assistance. Sometimes he had to figure it out as he went along. The recent Neo-Conning of the SSPX was certainly not his doing, nor is it the fault of the good religious and laity who would form the Resistance in reaction to it, many times as the result of undue expulsion from it. I sympathize with all the good people involved on each side, but the real answer must come from the very top. All of this is basic survival at the provisional level. We can barely maintain much less improve the situation.