Portal success? Not only do we not know how it will turn out in the end, we don't know why it has not been successful so far, nor do we know if the explanation has anything to do with being in a conference rather than, say, lack of preparation while the head coach flirted with the NFL.
I remind you conference team Alabama was left out last year and conference team FSU the year before. The conference couldn't save them. Political exclusion was enabled/required by ND losing its 2 games to its strongest opponents and the absurdity of the ACC's CCG tiebreaker, which stole an at large bid.
You suggest that a guaranteed bid to a conference champion would allow the players to participate in (the mythology of) "deciding it on the field." But the SEC, for one, wants to get rid of automatic bids. Would joining a conference come with a guarantee that would never happen? And when ND is only 1 voice in a conference, rather than representing itself in negotiations regarding the playoffs, what say would it have with respect to that.