But is it not a moral obligation for Catholics to be subject to the Pope?
Which pope are sedevacantists subject to at the moment? If it's a moral obligation, then wouldn't sedevacantism (except for the conclave period) be impossible?
I would think it follows that considering the status of the heretical, by-all-appearances-non-Catholic man who claims to be Pope, and whether or not you will "accept, recognize and obey [his] authority and supremacy" is a moral matter of the upmost importance.
If one (erroneously) believes that 99% of what a pope does, is subject to obedience, then your logic is sound. But not everything (and not most things) a pope does concerns some major, doctrinal or theological command. A lot of the what the pope does, is admin/govt stuff. Appointing new bishops, going over disputes, etc.
If a pope is a heretic, then we don't follow him. You either don't follow him, because a) you grasp the concept of ignoring a sinful command (R&R), or b) you ignore him because you say he has no authority (sedevacantism). The main difference between R&R and sedevacantism is one of
TIME.
R&R reject bad actions,
on a case by case basis, while still allowing for a pope to keep his authority (and, in theory, to
convert) in the future.
Sedevacantists
reject one, major bad action and reject the pope's authority now and in the future.
Both camps reject V2 errors, it's just a matter of how you deal with the aftermath. R&R think a heretic pope is allowed to regain his authority, by a conversion. Sedes do not. Neither of them "accept, recognize and obey" the pope. No Trad does. This isn't the "gotcha" question you think it is.