Sometimes I feel like sedevacantists, SSPX, and other tradcats bashing on Vatican II and Pope Francis aren’t really making Catholicism attractive to Eastern Orthodox Christians because they’re inadvertently sending the message that there’s no point to having a pope at all when they show that it’s perfectly acceptable to disrespect the Pope and split from the Church. And if they don’t accept Vatican II as a legitimate council as all the councils before then that’s like saying that the Holy Spirit abandoned the Catholic Church which goes against Matthew 16:18:
“And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it.”
The SSPX is a lot closer to us than the Eastern Orthodox Church but at the same time, just as you’re not bound to accept everything that Pope Francis says, there is still a limit to how far you can disagree with the Pope.
Fifth Lateran Council states:
"Moreover, since subjection to the Roman pontiff is necessary for salvation for all Christ's faithful, as we are taught by the testimony of both sacred scripture and the holy fathers, and as is declared by the constitution of pope Boniface VIII of happy memory, also our predecessor, which begins Unam sanctam, we therefore, with the approval of the present sacred council, for the salvation of the souls of the same faithful, for the supreme authority of the Roman pontiff and of this holy see, and for the unity and power of the church, his spouse, renew and give our approval to that constitution, but without prejudice to the declaration of pope Clement V of holy memory which begins Meruit."