There is an instructive post at NLM by Gregory DiPippo about Ecumencial Councils that failed but were, nonetheless, legitimate Ecumentical Councils.
Councils are called because there is a problem, not just for the heck of it. Or so it ought to be. Gregory uses the example of how the problem of clerics abusively holding multiple benefices had to be addressed. He explains what benefices are, btw. Lateran V addressed the problem of a plurality of benefices it but got the solution wrong (it still allowed four simultaneous benefices). That doesn’t make Lateran V a non-Council or illegitimate. The failure makes it a failed Council. Trent had to get the job done correctly down the line.
With that in mind, here are a couple of interesting paragraphs.
Here, then, is the second lesson to be drawn from this matter: it is perfectly possible for an ecumenical council (such as Lateran V) to correctly identify a problem within the Church (plurality of benefice), without correctly identifying the solution to that problem. Indeed, it is perfectly possible for said council to correctly identify a problem, and offer as a solution the exact opposite of what was needed to solve it, by de facto allowing it to continue. And it is perfectly possible to say this without denying the legitimacy of Lateran V as an ecumenical council.
Likewise, it is perfectly possible that Vatican II correctly identified a problem within the Church, the then-current state of its liturgical life, without correctly identifying the solution to that problem. Indeed, it is perfectly possible for said council to have correctly identified the problem, and offered as a solution the exact opposite of what was needed to solve it. (Of course, no two councils or the events that follow them are exactly alike, and so we must here once again note that the post-Conciliar reform is what it is in large measure because it rejected what Vatican II had said about the liturgy.) And it is perfectly possible to say this without denying the legitimacy of Vatican II as an ecumenical council.
Not all legitimate Councils were good. Not all succeeded in solving the problems of the day. Some solved some problems but not all. Some Councils failed. They are still legitimate Councils.
Not all priests, bishops or popes were or are good. Some fail. Some are even wicked.
Not all juridical and disciplinary decisions made by ecclesial authorities are good, simply by the fact that they were issued by an authority. Some are really bad. That doesn’t mean that the authority didn’t really have authority. Well… maybe he didn’t. My point is that just because an authority does something authoritative, that makes what he did good.
Our Church has a human dimension. That’s going to mean, over time, lots of screw ups and downright evil. The grace of orders does not overwhelm our fallen human nature and force men to become virtuous or intelligent. Vices can be overcome, of course, but stupid is forever.
It has ever been so. Happily, Our Lord knew this and, so, built in some fail safes to prevent total disaster.
Remember. Our Lord promised that Church would not fail, but He didn’t promise it would last in North Africa, Asia Minor, these USA or Vatican City.