Interesting that someone would "thumbs-down" the doctrine of the Church.
It implies a certain dishonesty in the sedevacantist position, if the latter cannot withstand these causes excusing from obedience to superiors.
If, like the FSSP, you could attempt to show why these arguments are not valid against a pope, that would be one thing (i.e., erroneous, but at least in good faith).
But to write off undisputed doctrines of the Church in order to maintain a position is another thing entirely, and not animated by a Catholic spirit.